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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Ocean Engineering and Technology
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Journal DOI :
Korean Society of Ocean Engineers
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Volume & Issues
Volume 17, Issue 6 - Dec 2003
Volume 17, Issue 5 - Oct 2003
Volume 17, Issue 4 - Aug 2003
Volume 17, Issue 3 - Jun 2003
Volume 17, Issue 2 - Apr 2003
Volume 17, Issue 1 - Feb 2003
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Application of Wavelet Transform to Problems in Ocean Engineering
KWON SUN-HONG ; LEE HEE-SUNG ; PARK JUN-SOO ;
Journal of Ocean Engineering and Technology, volume 17, issue 3, 2003, Pages 1~6
This study presents the results of series of studies, which are mainly devoted to the application of wavelet transforms to various problems in ocean engineering. Both continuous and discrete wavelet transforms were used. These studies attempted to solve detection of wave directionality, detection of wave profile, and decoupling of the rolling component from free roll decay tests. The results of these analysis, using wavelet transform, demonstrated that the wavelet transform can be a useful tool in analyzing many problems in the filed of ocean engineering.
Compatible Anchors of Silt Protector in Shallow Sea with Mud Seafloor Material
KWEON GI-CHUL ; HONG NAM-SEEG ; SONG Mu-HYO ; CHOI CHANG-GYU ;
Journal of Ocean Engineering and Technology, volume 17, issue 3, 2003, Pages 7~12
The Navy has tested the holding capacity of many kinds of anchors in order to propose the design chart for the holding capacity of drag-embedment anchors. The design chart is only applicable up to the cable bottom angle 60 when load is raised to the ultimate weight. However, the anchor experiences a significant uplift force when the angle is above 60 in shallow seas. In this paper, the procedure for the estimation of the holding capacity of anchors in mud is proposed. Drag-embedment anchors do not function well when there is a significant uplift component of load in soft seafloor materials, such as mud. Under these loading and seafloor conditions, gravity anchors seems to be more efficient. However, they are too heavy for their holding capacity. Therefore, suction pile (hollow concrete block) is more beneficial to the foundntion of silt protector in shallow sea with mud seafloor materials.
A Study on the Coast Topography using Real-Time Kinematics GPS and Echo Sounder
PARK WOON-YONG ; KIM JIN-SOO ; KIM CHEON-YEONG ;
Journal of Ocean Engineering and Technology, volume 17, issue 3, 2003, Pages 13~20
This research aims at investigation of accuracy potential of RTK(Real-Time Kinematic) GPS in combination with Echo Sounder(E/S) for the coastal mapping. Apart from this purpose, the accuracy of ambiguity resolution with the OTF(On The Fly) method was tested with respect to the initialization time. The result shows that the accuracy is better than 1cm with 5-minute initialization in the distance of 10km baseline. The seaside topography was measured by the RTK GPS only, on the other hand the seafloor topography was surveyed in combination of RTK GPS and E/S. Comparing to the volume of seaside measured by RTK GPS and digital topographical map, the difference of only
was achieved. This indicates that the coastal mapping. As a result, it has been revealed that every possible noise in surveying could be corrected and the accuracy could be improved. The accuracy of GPS data acquired in real time was as good as that acquired by post processing. It is expected that it will be useful for the analysis of coastal geographic characteristics because DTM(Digital Terrain Model) can be also constructed for the harbor reclamation, the dredging, and the variation of soil movement in a river.
Vibration Analysis of Thick Orthotropic Plates Using Mindlin Plate Characteristic Functions
LEE JONG-MOON ;
Journal of Ocean Engineering and Technology, volume 17, issue 3, 2003, Pages 21~26
An iteractive Kantorovich method is presented for the vibration analysis of rectangular orthotropic thick plates. Mindlin plate characteristic functions are derived in general forms using the Kantorovich method. Initially, Timoshenko beam functions consistent with the boundary conditions of the plate were used. Through numerical calculations of natural fairs of appropriate models, it has been confirmed that the method presented is superior to the Rayleigh-Ritz analysis or the finite element analysis in both accuracy and computational efficiency.
A Study on the Analysis of Welding Distortion for Moon Pool Structure of FPSO Vessel
KIM SANG-IL ;
Journal of Ocean Engineering and Technology, volume 17, issue 3, 2003, Pages 27~32
The welding distortion of a hull structure in the shipbuilding industry is inevitable at each assembly stage. The geometric inaccuracy caused by the distortion tends to preclude the introduction of automation and mechanization. Thus, additional man-hours are needed for the adjusting work in the assembly stage. To overcome this problem, a distortion control method should be applied. For this purpose, it is necessary to develop an accurate prediction method that can explicitly account for the influence of various factors on the welding distortion. In order to minimize the weld-induced residual deformation, this paper proposes the optimum welding sequence as a method for distortion control. The validity of this method has been substantiated by a number of numerical simulations and experiments.
Lifting Analysis for a Sunken Ship in Consideration of Elongation of Crane Ropes
CHOI KYUNG-SIK ; SHIN MAENG-KEE ;
Journal of Ocean Engineering and Technology, volume 17, issue 3, 2003, Pages 33~38
This study focuses on an analytical approach to calculate crane-lifting forces for a sunken ship, with consideration to elongation of crane ropes. The method takes into account the relation of lifting forces acting in wire rope slings to the inclination of the ship's hull, including the effect of lug positions. For lifting analysis, the Euler angles are defined to represent the inclination of a sunken ship in developing the static force and moment equations. An additional compatibility condition is introduced in order to solve an indeterminate lifting analysis problem with 4 cranes. A set of lifting forces along the 4 crane ropes is calculated. A 3-dimensional example of the G/T 1500 oil tanker is analyzed. The results show that the information obtained by the method could be useful to engineers when conducting salvage work.
Influence of Shot Peening on the Corrosion of Spring Steel
HA KYUNG-JUN ; PARK KYUNG-DONG ;
Journal of Ocean Engineering and Technology, volume 17, issue 3, 2003, Pages 39~45
Shot peening is an effective method of improving the fatigue strength of components and structures. The compressive residual stress produced by surface plastic deformation with shot peening is usually regarded as the major factor in increasing fatigue strength. In this study, the influence of shot peening on corrosion was investigated. Spring steel immersed in
NaCl prior was used to evaluate the effect of shot peening on fatigue properties. The immersion test was performed on the five kinds of specimens with shot peened and unpeened. The distributions of residual stresses of shot peened spring steels were measured in an X-ray diffraction apparatus, using the two-point method. Corrosion potential, polarization curve, residual stress, etc. were investigated, based on the experimental results. From test results, the effect of shot peening on the corrosion was evaluated.
Frequency Characteristics of Acoustic Emission Signal from Fatigue Crack Propagation in 5083 Aluminum by Joint Time-Frequency Analysis Method
NAM KI-WOO ; LEE KUN-CHAN ;
Journal of Ocean Engineering and Technology, volume 17, issue 3, 2003, Pages 46~51
Acoustic emission (AE) signals, emanated during local failure of aluminum alloys, have been the subject of numerous investigations. It is well known that the characteristics of AE are strongly influenced by the previous thermal and mechanical treatment of the sample. Possible sources of AE during deformation have been suggested as the avalanche motion of dislocations, fracture of brittle particles, and debonding of these particles from the alloy matrix. The goal of the present study is to determine if AE occurring as the result of fatigue crack propagation could be evaluated by the joint time-frequency analysis method, short time Fourier transform (STFT), and Wigner-Ville distribution (WVD). The time-frequency analysis methods can be used to analyze non-stationary AE more effectively than conventional techniques. STFT is more effective than WVD in analyzing AE signals. Noise and frequency characteristics of crack openings and closures could be separated using STFT. The influence of various fatigue parameters on the frequency characteristics of AE signals was investigated.
Corrosion Protection of STS304 Steel with Photo-Functional Material
NAM KI-WOO ; LEE SUNG-YEON ; AHN SEOK-HWAN ; KIM JONG-SOON ;
Journal of Ocean Engineering and Technology, volume 17, issue 3, 2003, Pages 52~56
This study investigates the photoelectrochemical behavior of STS304 steel with TiO2 thin films coating, applied by sol-gel mehod, for the purpose of cathodic photoprotection of the steel corrosion. One time TiO2-coated STS304 steel, adapted with two kinds of TiO2 sol solution, has the most dominant photopotential abilities, which was -200mV vs. SCE and -500mV vs. SCE under illumination with 40 W fluorescent lamp, respectively. That had yielded more negative values than the corrosion potential of the bare metal(-130mv vs.SCE). The bleaching of TCE was confirmed on TiO2-coated STS304 steel under UV-illumination with 20W Black-light. This Study concluded that Ti02-coated STS304 exhibited both a cathodic photoprotection effect against corrosion and a photocatalytic self-cleaning effect.