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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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International Journal of Ocean System Engineering
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Journal DOI :
Korean Society of Ocean Engineers
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Volume & Issues
Volume 3, Issue 4 - Nov 2013
Volume 3, Issue 3 - Aug 2013
Volume 3, Issue 2 - May 2013
Volume 3, Issue 1 - Feb 2013
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A New Approach to the Design of An Adaptive Fuzzy Sliding Mode Controller
Lakhekar, Girish Vithalrao ;
International Journal of Ocean System Engineering, volume 3, issue 2, 2013, Pages 50~60
DOI : 10.5574/IJOSE.2013.3.2.050
This paper presents a novel approach to the design of an adaptive fuzzy sliding mode controller for depth control of an autonomous underwater vehicle (AUV). So far, AUV's dynamics are highly nonlinear and the hydrodynamic coefficients of the vehicles are difficult to estimate, because of the variations of these coefficients with different operating conditions. These kinds of difficulties cause modeling inaccuracies of AUV's dynamics. Hence, we propose an adaptive fuzzy sliding mode control with novel fuzzy adaptation technique for regulating vertical positioning in presence of parametric uncertainty and disturbances. In this approach, two fuzzy approximator are employed in such a way that slope of the linear sliding surface is updated by first fuzzy approximator, to shape tracking error dynamics in the sliding regime, while second fuzzy approximator change the supports of the output fuzzy membership function in the defuzzification inference module of fuzzy sliding mode control (FSMC) algorithm. Simulation results shows that, the reaching time and tracking error in the approaching phase can be significantly reduced with chattering problem can also be eliminated. The effectiveness of proposed control strategy and its advantages are indicated in comparison with conventional sliding mode control FSMC technique.
Wave Spectrum Based Fatigue Analysis for Mediterranean Sea, Black Sea and Aegean Sea
Kabakcioglu, Fuat ; Bayraktarkatal, Ertekin ;
International Journal of Ocean System Engineering, volume 3, issue 2, 2013, Pages 61~67
DOI : 10.5574/IJOSE.2013.3.2.061
In this study, wave spectrum based fatigue analyses are studied for Turkey's adjacent coastal seas by using Maestro finite element analyzing software. Palmgren-Miner's method is used to obtain the fatigue safe life time. Palmgren-Miner's method was selected for the fatigue analyses because of its good acceptance of data from almost all classification societies such as Germanischer Lloyd, the American Bureau of Shipping, Det Norske Veritas, etc. The maximum stress regions of the structures are obtained by using finite element analyses, and the results are compared with the endurance limit of the W
hler diagram of AA5059 H321 aluminum alloy. The wave characteristics table given in this article is used to obtain the number of cycles for each sea condition. By using the wave characteristics table, the wave lengths, wave speeds, and cycles are obtained. This study is performed to estimate the lifetimes of a semi-swath type coast guard boat and/or commercial yacht projects, which are produced by using AA5059 H321 aluminum alloy, under different sea environment conditions. Fatigue examinations are performed for both head seas and oblique seas.
Nonlinear Wave Forces on an Offshore Wind Turbine Foundation in Shallow Waters
Choi, Sung-Jin ; Lee, Kwang-Ho ; Hong, Keyyoung ; Shin, Seong-Ho ; Gudmestad, O.T. ;
International Journal of Ocean System Engineering, volume 3, issue 2, 2013, Pages 68~76
DOI : 10.5574/IJOSE.2013.3.2.068
In this study, a 3D numerical model was used to predict nonlinear wave forces on a cylindrical pile installed in a shallow water region. The model was based on solving the viscous and incompressible Navier-Stokes equations for a two-phase flow (water and air) model and the volume of fluid method for treating the free surface of water. A new application was developed based on the cut-cell method to allow easy installation of complicated obstacles (e.g., bottom geometry and cylindrical pile) in a computational domain. Free-surface elevation, water particle velocities, and inline wave forces were calculated, and the results show good agreement with experimental data obtained by the Danish Hydraulic Institute. The simulation results revealed that the proposed model can, without the use of empirical formulas (i.e., Morison equation) and additional wave analysis models, reliably predict non-linear wave forces on an offshore wind turbine foundation installed in a shallow water region.
On Propeller Performance of DTC Post-Panamax Container Ship
Kinaci, Omer Kemal ; Kukner, Abdi ; Bal, Sakir ;
International Journal of Ocean System Engineering, volume 3, issue 2, 2013, Pages 77~89
DOI : 10.5574/IJOSE.2012.3.2.077
The propeller performance has been investigated using a benchmark Duisburg Test Case ship with RANSE. First, the hydrodynamic characteristics of propeller in case of open water have been analyzed by a commercial CFD program and the results are compared with those of experimental data. Later, the flow around the bare hull has been solved and the frictional resistance value and form factor of the ship have been obtained and compared with those of ITTC57 formulation and experimental results for validation. The free surface effect has been ignored. A good agreement has been obtained between the results of RANSE and experiments at both stages. Then the ship - propeller interaction problem was solved by RANSE and the differences in thrust, torque and efficiency of propeller as compared with the open-water numerical results have been discussed.
Distribution of Cathodic Protection Potential for Concrete Slab Specimens at Diverse Environmental Conditions
Jin, Chung-Kuk ; Jeong, Jin-A ;
International Journal of Ocean System Engineering, volume 3, issue 2, 2013, Pages 90~94
DOI : 10.5574/IJOSE.2013.3.2.090
This study represents the recent laboratory results from cathodic protection (CP) system with the use of sacrificial anodes at different environmental conditions (temperature of
). Specimens were slab type with a dimension of
, and concrete cover thickness were 25mm. Zinc mesh and/or bulk type anodes were installed at the center of specimen to confirm the distance that CP system has influences on the specimen to distribute uniform CP current to rebar. Two different kinds of temperature condition were applied to verify the effect of temperature. Experiments were conducted for 60 days, and the distribution of potential and current that supplied from anode to rebar was measured. From the results, CP potential was varied with time, and temperature played an important role in CP potential variations. Current was also changed with time, and current distribution could be improved by installing additional bulk type anode.
Thermal Distortion Analysis by Inconel Over-Lay At Circular Moonpool Structures
Ha, Yunsok ;
International Journal of Ocean System Engineering, volume 3, issue 2, 2013, Pages 95~101
DOI : 10.5574/IJOSE.2013.3.2.095
This study is mainly interested in roundness of a circular moonpool structure in FPSO. Because this structure needs abrasion-resistance on inner wall, we should do buttering widely and deeply by using Inconel. But a general buttering can cause a severe distortion at structures. If someone can analyze the roundness by thermal distortion under Inconel over-lay, an erection policy can be established. In this study, shrinkage methodology by designed stress-strain curve was used and the result allowed deciding an appropriate block size.
Study on Mechanical and Thermal Properties of Tio
/Epoxy Resin Nanocomposites
Kim, Bu-Ahn ; Moon, Chang-Kwon ;
International Journal of Ocean System Engineering, volume 3, issue 2, 2013, Pages 102~110
DOI : 10.5574/IJOSE.2013.3.2.102
The purpose of this study was to improve the properties of epoxy resin using titanium oxide nanoparticles. The effects of particle weight fraction, dispersion agent, and curing agents with different molecular weights on the thermal and mechanical properties of titanium-oxide-reinforced epoxy resin were investigated. In addition, the effect of the particle dispersion condition on the mechanical properties of nanocomposites was studied. As a result, it was found that the glass transition temperature of film-shaped nanocomposites decreased with an in-crease in the nanoparticle content. Because nanoparticles interrupted the cross linkage between the epoxy resin and the amine curing agent, the cross-link density of the epoxy became lower and led to a decrease in
in the nanocompo-sites. The tensile strength and modulus in film-shaped nanocomposites also increased with the particles content. But in the case of dog-bone-shaped nanocomposites, the values were not similar to the trend for the film-shaped nanocompo-sites. This was probably a result of the different nanoparticles dispersions in the epoxy resins resulting from the respective-thicknesses of the film and dog-bone-shaped samples.