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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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Experimental Investigation of Drag Reduction by Polymer Additives
Journal of Ocean Engineering and Technology, volume 16, issue 4, 2002, Pages 1~6
Experimental investigation of drag reduction by adding a polymer additive(polyacrylamid, N-401P) into water is carried out in a Circular Water Channel. The effect of viscosity, surface roughness and degradation as a function of running time is also measured with varying the concentration of polymer additives(20ppm,100ppm) and Reynolds numbers. Near and far wakes past a circular cylinder are observed by LDV. Drag forces are measured with a strain-gaged device. The experimental results show that around 5%-30% of drag reduction with the polymer solution are observed. The larger effects of drag reduction can be found at low range of Reynolds number, more roughened surface cylinder. The effect of polymer solution for near wakes is larger than for far wakes.
Scouring Characteristics at the Toe of the Rubble Mound Breakwater
Journal of Ocean Engineering and Technology, volume 16, issue 4, 2002, Pages 7~12
This study is aimed to find the scouring mechanism at the toe of rubble mound structures. To investigate the characteristics of scouring in front of the structure, experiments were performed with regular waves in a 2-D flume. The results of this study are as follows. 1) It can be said the characteristics of incident wave causes rolling and sliding of armour block. The difference of wave pressure on the slope, internal flow as well as settlement of armour block due to the weight cause scouring. 2) It is observed that scouring depth at the toe increased when wave height or period increased. The location of ultimate scouring and deposition depth moved seaward when wave period increased. 3) The failure of rubble mound structure was caused by waves or scouring. Failure by erosion increased with high waves and long waves. 4) Using surf-similarity parameter including characteristics of incident waves and structure, scouring and deposition pattern were found and their limit was formulated.
A Study on the Measurement of Elastic-Plastic Zone at the Crack Tip under Cyclic Loading using ESPI System
Journal of Ocean Engineering and Technology, volume 16, issue 4, 2002, Pages 13~18
The magnitude of the plastic zone around the crack tip of DENT(Double Edge Notched Tension) specimen and the crack growth length under cyclic loading were measured by ESPI(Electronic Speckle Pattern Interferometry) system. The measured magnitude of plastic zone was compared with the equations proposed by Irwin and calculated by a nonlinear static method of MSC/NASTRAN. The measured crack growth length by ESPI system was also compared with the obtained data by the image analysis system. From the study, it is confirmed that the plastic zone and crack growth length can be measured accurately with the high-tech equipment.
A Study on the Pit Excavation Volume Using Cubic B-Spline
Du-Yeoul Mun ;
Journal of Ocean Engineering and Technology, volume 16, issue 4, 2002, Pages 19~24
Discrete Optimization of Plane Frame Structures Using Genetic Algorithms
Journal of Ocean Engineering and Technology, volume 16, issue 4, 2002, Pages 25~31
This paper is to find optimum design of plane framed structures with discrete variables. Global search algorithms for this problem are Genetic Algorithms(GAs), Simulated Annealing(SA) and Shuffled Complex Evolution(SCE), and hybrid methods (GAs-SA, GAs-SCE). GAs and SA are heuristic search algorithms and effective tools which is finding global solution for discrete optimization. In particular, GAs is known as the search method to find global optimum or near global optimum. In this paper, reinforced concrete plane frames with rectangular section and steel plane frames with W-sections are used for the design of discrete optimization. These structures are designed for stress constraints. The robust and effectiveness of Genetic Algorithms are demonstrated through several examples.
Health Monitoring of Weldment By Post-processing Approach Using Finite Element Analysis
Journal of Ocean Engineering and Technology, volume 16, issue 4, 2002, Pages 32~36
In this paper, a numerical methodology for health monitoring of weldment was proposed using finite element method coupled with continuum damage mechanics. The welding-induced residual stress distribution of T-joint weldment was calculated using a commercial finite element package SYSWELD+. The distribution of latent damage was evaluated from the stress and strain components taken as the output of a finite element calculation. Numerical examples were given to demonstrate the usefulness of this so-called "post-processing approach" in the case of welding-induced damage assessment.
A Structural Analysis of Aluminum Heli-Deck
Lee, Jae-Hwan ; Chung, Tae-Hwan ;
Journal of Ocean Engineering and Technology, volume 16, issue 4, 2002, Pages 37~41
A Study on Mode II Interlaminar Fracture Toughness of Hybrid Composites
Journal of Ocean Engineering and Technology, volume 16, issue 4, 2002, Pages 42~47
This paper describes the effect of loading rate, specimen geometries and material properties for Mode II interlaminar fracture toughness of hybrid composite by using end notched flexure(ENF) specimen. In the range of loading rate 0.5~2mm/min, there is found to be no significant effect of loading rate with the value of critical energy release rate(
). there is no dependence of the interlaminar fracture energy upon the specimen width over the specimen widths examined. The value of
for variation of initial crack length are nearly similiar values when material properties are CF/CF and GF/GF, however, the value of
are highest with the increasing intial crack length at CF/GF. The values of
for variation material properties are higher with the increasing moulding pressure when moulding pressures are 307, 431, 585㎪. The SEM photographs show good fiber distribution and interfacial bonding of hybrid composites when the moulding is the CF/GF.e CF/GF.
Characteristics of Elastics Waves of Fiber-Reinforced Plastic with Localized Heat Damage
Journal of Ocean Engineering and Technology, volume 16, issue 4, 2002, Pages 48~53
Fiber-reinforced composites are extensively used in electronic, ship and aerospace applications due to their high strength and high toughess. In these applications, they are often subjected to localized heat damage due to various sources. In order to ensure their reliability, it is important to predict their residual properties using nondestructive evaluation thchniques. Fabric fiber composite specimens were manufactured with six layers of the glass-fiber prepreg and the carbon-fiber prepreg, respectively. The specimens were subjected to a localized heat damage using a heated copper tip with a diameter of 10mm at 35
(CFRP) and 30
(GFRP), respectively. The specimens were then subjected to tension tests while acoustic emission (AE) activities of specimens were collected. The AE activity of all specimens showed three types of distinct frequency regions. Those are matrix cracking, failure of the fiber/matrix interface and fiber breakage.
Design and Analysis of Dynamic Positioning System Using a Nonlinear Robust Observer
Myung-Hyun Kim ;
Journal of Ocean Engineering and Technology, volume 16, issue 4, 2002, Pages 54~60
Anti-Windup Controller Design for the Ship with the Rudder Saturation
Journal of Ocean Engineering and Technology, volume 16, issue 4, 2002, Pages 61~69
In the actual control systems, there exist many kinds of restrictions or nonlinearities. However, due to the nonlinearities in actuators and sensors, the designed controller may not be applicable in some practical situations. One such nonlinearity is amplitude saturation in actuators. Although sometimes it may be ignored, in other cases failure to consider actuator saturation may severely degrade closed-loop system performance and even lead to instability. On the other hand, limiting the controller gain to avoid saturation sacrifices control effort and may lead to loss of performance. Consequently, in some cases, the actuator saturation must be explicitly taken into account to ensure desired performance. However, in this paper, an anti-windup control system design method is introduced to suppress the windup due to the amplitude saturation of the actuator. The proposed control system has very simple design process and guarantees the good control performance. The validity of the proposed control system will be shown by comparing with the results of a reported paper.