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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 20, Issue 6 - Dec 2006
Volume 20, Issue 5 - Oct 2006
Volume 20, Issue 4 - Aug 2006
Volume 20, Issue 3 - Jun 2006
Volume 20, Issue 2 - Apr 2006
Volume 20, Issue 1 - Feb 2006
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Active Control of Offshore Structures for Wave Response Reduction Using Probabilistic Neural Network
Kim, Doo-Kie ; Kim, Dong-Hyawn ; Chang, Sang-Kil ; Chang, Seong-Kyu ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 1~8
Offshore structures are subjected to wave, wind, and earthquake loads. The failure of offshore structures can cause sea pollution, as well as losses of property and lives. Therefore, safety of the structure is an important issue. The reduction of the dynamic response of offshore towers, subjected wind generated random ocean waves, is a critical problem with respect to serviceability, fatigue life and safety of the structure. In this paper, a structural control method is proposed to control the vibration of offshore structures by the probabilistic neural network (PNN). The state vectors of the structure and control forces are used for training patterns of the PNN, in which control forces are prepared by linear quadratic regulator (LQR) control algorithm. The proposed algorithm is applied to a fixed offshore structure under random ocean waves. Active control of the fixed offshore structure using the PNN control algorithm shows good results.
Integrated Expansion Analysis of Pipe-In-Pipe Systems
Choi, Han-Suk ; Do Chang-Ho ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 9~14
This paper presents an analytical method, application of expansion, mechanical design, and integrated expansion design of subsea insulated pipe-in-pipe (PIP) systems. PIP system consists of a flowline and a casing pipe for the transport of high temperature and high pressure product from the subsea wells. To prevent heat lass from the fiowline, insulation material is applied between the pipes. The fiawline pipe and the casing pipe have mechanical connections through steel ring plate (water stops) and bulkheads. Pipeline expansion is defined by temperature, internal pressure, soil resistance, and interaction force between the flowline and the casing pipe. The results of the expansion analysis, the mechanical design of connection system of the two pipes and tie-in spool design are integrated for the whole PIP system.
Characteristics of Laminar Wake Around Two-Circular Cylinder in Side-by-Side Array
Lee, Sang-Beom ; Park, Jong-Chun ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 15~22
A finite-volume method using multi-block grid technique has been developed in order to investigate the flow field around multi-body. Here the matching grids are used at the interface between blocks and the boundary conditions are imposed there to exchange physical values across the interface. For the test problems, the laminar viscous flaw around one-and two-cylinder are simulated and the results are compared with experiments and other numerical results.
Numerical Analysis of Wind Driven Current and Mesoscale Air Flow in Coastal Region with Land Topography
Lee, Seong-Dae ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 23~29
A quasi depth-varying mathematical model for wind-generated circulation in coastal areas, expressed in terms of the depth-averaged horizontal velocity components and free surface elevation was validated and used to understand the diurnal circulation process. The wind velocity is considered as a dominant factor for driving the current. In this paper, three-dimensional numerical experiments that included the land topography were used to investigate the mesoscale air flaw over the coastal regions. The surface temperature of the inland area was determined through a surface heat budget consideration with the inclusion of a layer of vegetation.A series of numerical experiments were then carried out to investigate the diurnal response of the air flaw and wind-generated circulation to various types of surface inhomogeneities.
Nonlinear Response Characteristics of the ISSC TLP in Time Domain
Lee, Chang-Ho ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 30~35
In tire presence of incident waves with different frequencies, there are second order sum and difference frequency wave exciting forces due to the nonlinearity of tire incident waves. Although the magnitude of these nonlinear wave forces are small, they act on TLPs at sum and difference frequencies away from those of the incident waves. So, the second order sum and difference frequency waveexciting forces occurring close to tire natural frequencies of TLPs often give greater contributions to high and law frequency resonant responses. Nonlinear motion responses and tension variations in the time domain are analyzed by solving the motion equations with nonlinear wave exciting forces using tire numerical analysismethod. The numerical results of time domain analysis for the nonlinear wave exciting forces on the ISSC TLP in regular waves are compared with the numerical and experimental ones of frequency domain analysis. The results of this comparison confirmed tire validity of the proposed approach.
Time Domain Analysis of a Tension Leg Platform in Multi-Directional Irregular Waves
Lee, Chang-Ho ; Kim, Chuel-Hyun ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 36~41
The main object of this study is to develop an accurate and convenient method for the response analysis of offshore structures in real sea states. A numerical procedure is described for predicting the motion responses and tension variations of the ISSC TLP in multi-directional irregular waves. The developed numerical approach in the frequency domain is based on acombination of the three dimensional source distribution method, the dynamic response analysis method, and the spectral analysis method. Frequency domain analysis in the multi-directional irregular waves is expanded to a time domain analysis by using a convolution integral after obtaining the impulse response by Fourier transformation. The results of the comparison between responses in the frequency and time domain confirmed the validity of the proposed approach.
Centrifuge Model Tests on Characteristics in Forced Replacement Method for Soft Ocean Ground to Build Coastal Structures
Park, Byung-Soo ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 42~48
This paper shows theresults of centrifuge model experiments to investigate the behavior of a replacement method in dredged and reclaimed ground. For this experimental work, centrifuge model tests were carried out to investigate the behavior of a replacement method in soft clay ground. Basic soil property tests were performed to find the mechanical properties of clay soil sampled from the southern coast of Korea, which was used for the ground material in the centrifuge model tests. The reconstituted clay ground of the model was prepared by applying reconsolidntion pressure in a 1 g condition with a specially built model container. Centrifuge model tests were carried out under the artificially accelerated gravitational level of 50 g. Replacement material of lead with a certain degree of angularity was used and placed until the settlement of the replacement material embankment reached a state of equilibrium. Vertical displacement of the replacement material was monitored during tests. The depth and shape of the replacement, especially the slope of the penetrated material and the water content of the clay ground were measured after finishing tests. Model tests for investigating the stability of an embankment after backfilling were also performed to simulate the behavior of a dike treated with replacement and backfilled with sandy material. As a result of the centrifuge model test, the behavior of the replacement, the mechanism of the replacement material being penetrated into clay ground, and the depth of the replacement were evaluated.
Centrifuge Model Experiments and Numerical Analyses of the Behavior of Excavated Marine Clay Slope
Park, Byung-Soo ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 49~56
In this thesis, centrifuge model experiments and numerical analyses were carried out to investigate the behavior of an excavated slope in soft clay ground. Centrifuge model tests were performed with various slopes for the excavated ground, such as 1:1.5 and 1:2. Pore pressuresthe model ground were measured to find their effects on the stability of the excavated slope. These experiments showed that the model with 1:2.5 maintained its stability within a short period of time and failed gradually. Therefore, anexcavated slope of soft soil with this slope might maintain stable conditions within a certain time. The mode1 with a 1:3 slope was observed to maintain a very stable condition, showing insignificant deformation in the ground after being excavated. Numerical analyses with PLAXIS, a commerciallyavailable software implemented with the finite element numerical technique, were performed to find the pore pressure distribution within the ground mass and the deformation of the soil. From the results of numerical analysis, a negative pore pressure was developed after the excavation and thus the stability of the slope was maintained. The safety factor for slope failure was found to decrease with time because of the dissipation of negative pore pressure with time.
An Experimental Study on the Accurate Tracking Control of a Transfer Crane Based on the 2DOF Servosystem Design Approach
Kim, Young-Bok ; Lee, Kwon-Soon ; Han, Seong-Hoon ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 57~62
The most important thing in acontainer terminal is to handle the cargo effectively in the limited time available. To achieve this objective, many strategies have been introduced and applied. To create an automated container terminal, it is necessary for the cargo handling equipment to be equipped with more intelligent control systems. From the middle of the 1990's, automated rail-mounted gantry cranes (RMGC) and rubber-tired gantry cranes (RTG) have been widely used to handle containers in yards. Recently, many pieces of equipment, like CCD cameras and sensors, have beenmounted in these cranes to cope with the automated terminal environment. In this paper, we try to support the development of more intelligent automated cranes, which allow for more effective cargo handling in yards. For this purpose, the modeling, tracking control, anti-sway system design, skew motion suppressing, and complicated motion control and suppressing problems must be considered. Especially, in this paper, the system modeling and a new tracking control approach are discussed, and an experimental study is performed based on a two-degree-of-freedom (2DOF) servosystem design.
Pounding Mechanism and Mitigation Effect of Pounding between Adjacent Decks during Strong Earthquake
Kwon, Young-Rog ; Kim, Jin-Woo ; Choi, Kwang-Kyu ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 63~69
An isolated bridge using a laminated rubber bearing provides an elastic support of continuous span and prevents the transmission of excessive seismic force from the substructure of the bridge, which uses a metal bearing, as this permits a relative displacement between the super-and substructure. Hawever, this kind of bridge is caused long periodic, as a result of enlargingtotal thickness of the rubber, since it corresponds to temperature change and increases the horizontal displacement of the superstructure. This paper uses a numerical study to describe the pounding problem between adjacent decks when subjected to a strong earthquake. Furthermore, numerical results are clarified for the buffer rubber used to mitigate the pounding force between adjacent decks.
Estimation of the Stability Number of Breakwater Armor Blocks Using Probabilistic Neural Networks
Kim, Doo-Kie ; Kim, Dong-Hyawn ; Chang, Seong-Kyu ; Chang, Sang-Kil ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 70~76
A Probabilistic neural network (PNN) technique for predicting the stability number for the armor blocks of breakwaters is presented. A PNN is prepared using the experimental data of van der Meer and is then compared with the empirical formula and previous artificial neural network (ANN) model. This comparison shows that a PNN can effectively predict the stability numbers in spite of data complexity, incompleteness, and incoherence, and can be an effective tool for the designers of rubble mound breakwaters to support their decision process and to improve design efficiency.
Microstructure Effects on Bending Strength Characteristics of LPS - SiC Ceramic
Yoon, Han-Ki ; Jung, Hun-Chae ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 77~81
In this study, monolithic liquid phase sintered SiC (LPS-SiC) was made by the hot pressing method with nano-SiC powder, whose particle size is 30 nm and less on the average. Alumina (
), yttria (
), and silica (
) were used for sintering additives. To investigate the effects of
composition was fixed and the ratio of
was changed, with seven different ratios tested. And to investigate the effects of the sintering temperature, the sintering temperature was changed, with
being used with a
ratio of 3 wt%. The materials were sintered for 1 hour at
under a pressure of 20 MPa. The effects on sintering from the sintering system used, as well as from the composition of the sintering additives, were investigated by density measurements. Mechanical properties, such as flexural strength, were investigated to ensure the optimum conditions for a matrix of SiCf/SiC composites. Sintered densityand the flexural strength of fabricated LPS-SiC increased with an increase in sintering temperature. Particularly, the relative density of a sintered body at
with a non-content of
, a specimen of AYSO-1800, was 95%. Also, flexural strength was about 750MPa.
Assessment of Fatigue Strength Characteristics of Tendon Porch in Offshore Platforms for API 2W Gr. 50 Steel
Im, Sung-Woo ; Lee, Joo-Sung ;
Journal of Ocean Engineering and Technology, volume 20, issue 5, 2006, Pages 82~88
This assessment is concerned with the fatigue strength of the tendon porch found in TLP. Lorge-scale fatigue tests with models constructed at 30% the size of the real structures have been carried out to investigate the fatigue behavior of the API 2W Grade 50 steel recently produced by POSCO. The fatigue life for the present test models was obtained based on the concept of nominal stress. A comparison of the present test results with those obtained by a numerical approach based on the structural analysis results has showngood agreement. The present results were also compared with the design curves in DnV RP-C203.