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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Ocean Engineering and Technology
Journal Basic Information
Journal DOI :
Korean Society of Ocean Engineers
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Volume & Issues
Volume 16, Issue 6 - Dec 2002
Volume 16, Issue 5 - Oct 2002
Volume 16, Issue 4 - Aug 2002
Volume 16, Issue 3 - Jun 2002
Volume 16, Issue 2 - Apr 2002
Volume 16, Issue 1 - Feb 2002
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An Experimental Study on Wave Focusing Efficiency in the Generation of Directional Extreme Waves
Journal of Ocean Engineering and Technology, volume 16, issue 5, 2002, Pages 1~6
Extreme waves are generated in a model basin based on directional wave focusing. The targeted wave field is described by double summation method and it is applied to serpent-type wavemaker system. The extreme crest amplitude at a designed location is obtained by syncronizing the phases and focusing the directions of wave components. Two distinguished spectrums of constant wave amplitude and constant wave steepness are adapted to describe the frequency distribution of component waves. The surface profile of generated wave packets is measured by wave guage array and the effects of dominant spectral parameters governing extreme wave characteristics are investigated. It is found that frequency bandwidth, center frequency, shape of frequency spectrum and directional range play a significant role in the wave focusing. In particular, the directional effect significantly enhances the wave focusing efficiency.
Submerged Membrane Breakwaters I: A Rahmen Type System Composed of Horizontal and Vertical Membranes
Journal of Ocean Engineering and Technology, volume 16, issue 5, 2002, Pages 7~14
in the present paper, the hydrodynamics properties of a Rahmen type flexible porous breakwater interacting with obliquely or normally incident small amplitude waves are numerically investigated. This system is composed of dual vertical porous membranes hinged at th side edges of a submerged horizontal membrane. The dual vertical membranes are extended downward and hinged at seabed. The effects of permeability, Rahmen type membrane breakwater geometry pre-tensions on membranes, relative dimensionless wave number, and incident Wave headings are thoroughly examined.
Study on Analysis of Gravity Currents by the Finite Difference Boltzmann Method using Two-dimensional Compressible fluid Model
Journal of Ocean Engineering and Technology, volume 16, issue 5, 2002, Pages 15~20
In this research, the finite difference lattice Boltzmann method(FDLBM) is used to analyze gravity currents in the lock exchange configuration that occur in many natural and man-made situations. At a lock those are seen when a gate is suddenly opened, and, in the atmosphere, when the thunderstorm outflows make a cold front. At estuaries in the ocean, the phenomenon is found between fresh water from a river and salt water in the sea. Since such interesting phenomena were recognized, pioneers have challenged to make them clear by conducing both experiments and analysis. Most of them were about the currents of liquid or Boussinesq fluids, which are assumed as incompressible. Otherwise, the difference in density of two fluids is small. The finite difference lattice Boltzmann method has been a powerful tool to simulate the flow of compressible fluids. Also, numerical predictions using FDLBM to clarify the gravity currents of compressible fluids exhibit all features, but typically observed in experimental flows near the gravity current head, including the lobe-and-cleft structure at the leading edge.
Effects of Dynamic Soil Behaviour on Wave-Induced Seabed Response
Cha, D.H ; Jeng, D.S ; Rahman, M.S. ; Sekiguchi, H. ; Zen, K. ; Yamazaki, H. ;
Journal of Ocean Engineering and Technology, volume 16, issue 5, 2002, Pages 21~33
In this paper, an analytical solution for the wave-induced seabed response in a porous seabed is derived. Unlike previous investigations with quasi-static soil behaviour, dynamic soil behaviour is considered in the new solution. The basic one-dimensional framework proposed by Zienkiewicz et al (1980) is extended to two-dimensional cases. Based on the analytical solution derived, the effects of dynamic soil behaviour on the wave-induced seabed response are examined. The boundary of quasi-static soil behaviour and dynamic soil behaviour is clarified, and formulated for engineering practice.
Numerical Modeling of Wave Run-up and Internal Set-up on and in Permeable Coastal Structures
Journal of Ocean Engineering and Technology, volume 16, issue 5, 2002, Pages 34~40
A numerical model has been developed for the permeable coastal structures to simulate hydraulic characteristics on the permeable slopes, which interact with internal four field the structures. The model includes hydraulics in the porous medium. Numerical model was calibrated using hydraulic model experiments performed in 2-D wave flume in the Institute of Ocean Hydraulics in PKNU. Better aggrements were obtained with the model which employed inertia resistance term than with the conventional model, PBREAK.
Importance of the Settling Velocity on the Suspended Solids Diffusion in Osaka Bay
Journal of Ocean Engineering and Technology, volume 16, issue 5, 2002, Pages 41~48
Numerical experiments are conducted using a three-dimensional baroclinic equation model and a Lagrangian method for clarifying the effect of th settling velocity on the suspended solids diffusion caused by the dredging and the reclamination works. Diffusion characteristics of the neutral particles and the weighting particles is experimented by the Lagrangian particles trajectory model, The results show that the diffusion characteristics of the suspended solids is effected by the settling velocity classified by the particles size in the density layered semi-closed bay. To estimate exactly the diffusion characteristics of the suspended solids and the contaminant with weight the three-dimensional baroclinic equation model and the three-dimensional Lagrangian particles trajectory model considering the settling velocity of the particle in the density layered semi-closed bay must be used.
Analysis on Reinforcing Effect at Fixed Part of Compression Anchor by Laboratory Element Tests
Journal of Ocean Engineering and Technology, volume 16, issue 5, 2002, Pages 49~55
The compression anchor is characterized by decrement of progressive failure, simple site work, economy and durability compared with tension anchor. In this paper, compression anchor is analysed through the laboratory element tests. The formula to be estimate the grout strength in fixed part of compression anchor and the effective reinforcement method for several types of soil were suggested. The following conclusions were made from this study : (1) A formula, which is able to calculate the grout strength in the fixed part of the compression anchor, is suggested. (2) The strength increment ratios(
) are 100％, 132％, 147％, 217％ according to the reinforcement method of grout. The reinforcement method is Non, Outside spiral, Inside-Outside spiral, Steel pipe, respectively. (3) The strength increment ratios(
) by reinforcing can be 8.23 times the strength increment effect according to the reinforcement types and ground confining pressure. (4) The steel pipe reinforcement is most effective in decomposed soil while, in the case of hard rock ground, high confining pressure is exerted on the grout, so there is no need to use reinforcements.
Expansion Analysis of Subsea Pipe-In-Pipe Due to High Temperature and High pressure Product
Journal of Ocean Engineering and Technology, volume 16, issue 5, 2002, Pages 56~60
Fault Diagnosis of Rotating Machines Using Wavelet Transform and Neural Network
Journal of Ocean Engineering and Technology, volume 16, issue 5, 2002, Pages 61~65
The fault detection and diagnosis of rotating machinery widely used in plants including the ship are important for maintaining the performance of Plants. Recently, the wavelet transform has been recognized an efficient method to detect a little variation of physical quantities by the synchronous localization of time and frequency domains using the translation and dilation of signals. In this Paper, In order to develop efficient and reliable fault detection and diagnosis system rotating machines, the performance of wavelet transformation to detect a little variation of machine status and neural network to diagnose the cause of machine faults are investigated and experimented.
Acoustic Emmision Characteristics according to Failure Modes of Pipes with Local Wall Thinning
Journal of Ocean Engineering and Technology, volume 16, issue 5, 2002, Pages 66~72
Fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear power plant. However, effects of local wall thinning on strength and fracture behaviors of piping system were not well studied. Acoustic emission(AE) has been widely used in various fields because of its extreme sensitivity, dynamic detection ability and location of growing defects. In this study, we investigated failure modes of locally wall thinned pipes and AE signals by bending test. From test results, we could be divided four types of failure modes of ovalization, crack initiation after ovalization, local buckling and crack initiation after local buckling. And fracture behaviors such as elastic region, yielding region, plastic deformation region and crack progress region could be evaluated by AE counts, accumulative counts and time-frequency analysis during bending test. The result of the frequency range is expected to be basic data that can inspect plants in real-time.
Effect of Compressive Residual Stress on the High Temperature fatigue Crack Propagation Behavior of Shot-peened Spring Steel
Journal of Ocean Engineering and Technology, volume 16, issue 5, 2002, Pages 73~79
In this paper, the effect of the compressive residual stresses was obtained at the test conditions of the higher temperature than the ambient temperature. The examination was performed with the CT specimen result of the material(JISG SUP9) which is being commonly used for the marine engine parts and the ocean structures. As a result, the test conditions at the higher temperature were acquired considering the peak values of the compressive residual stresses of the specimens and the effect on the fatigue crack propagation speed da／dN in stage II and the threshold stress intensity factor range Δth in stage I. Also the material constant C and the fatigue crack propagation index m in the formula of Paris Law da／dN＝C (ΔK)
were suggested to estimate the dependence on the test temperature.
A Study on the Fatigue Crack Propagation Characteristics for SUP9 Steel at Low Temperature
Journal of Ocean Engineering and Technology, volume 16, issue 5, 2002, Pages 80~87
In this study, CT specimens were prepared from spring steel(SUP9) which was used in suspension of automobile for room temperature and low temperature service. We got the following characteristics from fatigue crack growth test carried out in the environment of room temperature and low temperature at
in the range of stress ratio of 0.05 by means of opening mode displacement. The threshold stress intensity factor range ΔKth in the early stage of fatigue crack growth (Region I) and stress intensity factor range ΔK in the stable of fatigue crack growth (Region II) was decreased in proportion to descend temperature. It is assumed that the fatigue resistance characteristics and fracture strength at low temperature and high temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region.