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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 23, Issue 6 - Dec 2009
Volume 23, Issue 5 - Oct 2009
Volume 23, Issue 4 - Aug 2009
Volume 23, Issue 3 - Jun 2009
Volume 23, Issue 2 - Apr 2009
Volume 23, Issue 1 - Feb 2009
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2D Computational Analysis of Overtopping Wave Energy Convertor
Liu, Zhen ; Hyun, Beom-Soo ; Jin, Ji-Yuan ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 1~6
An Overtopping Wave Energy Convertor (OWEC) is an offshore wave energy convertor used for collecting overtopping waves and converting the water pressure head into electric power through hydro turbines installed in a vertical duct affixed to the sea bed. A numerical wave tank based on the commercial computational fluid dynamics code Fluent is established for the corresponding analysis. The Reynolds Averaged Navier-Stokes equation and two-phase VOF model are utilized to generate the 2D numerical linear propagating waves, which are validated by the overtopping experiment results. Calculations are made for several incident wave conditions and shape parameters for the overtopping device. Both the incident wave periods and heights have evident effects on the overtopping performance of the OWEC device. The computational analysis demonstrates that the present overtopping device is more compatible with longer incident wave periods.
A Hydroelastic Analysis of a Floating Fish Cage in Waves
Choi, Yoon-Rak ; Yeo, Hwan-Tae ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 7~11
The dynamic responses and drift forces in waves of a floating circular fish cage are analyzed considering hydroelastic effects. The method of generalized mode is used to calculate the hydroelastic responses of the floater of cage. The elastic mode shapes, generalized mass, and stiffness in dry mode are evaluated by using a structural analysis code. The higher-order boundary element method is adopted to analyze the interaction between fluid and deformable structure. Some results of vertical motions and drift forces are shown and compared with those for a rigid body.
Spatial Modulation of Nonlinear Waves and Their Kinematics using a Numerical Wave Tank
Koo, Weon-Cheol ; Choi, Ka-Ram ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 12~16
In this study, the wave profiles and kinematics of highly nonlinear waves at various water depths were calculated using a 2D fully nonlinear Numerical Wave Tank (NWT). The NWT was developed based on the Boundary Element Method (BEM) with the potential theory and the mixed Eulerian-Lagrangian (MEL) time marching scheme by 4th-order Runge-Kutta time integration. The spatial variation of intermediate-depth waves along the direction of wave propagation was caused by the unintended generation of 2nd-order free waves, which were originally investigated both theoretically and experimentally by Goda (1998). These free waves were induced by the mismatch between the linear motion of wave maker and nonlinear displacement of water particles adjacent to the maker. When the 2nd-order wave maker motion was applied, the spatial modulation of the waves caused by the free waves was not observed. The respective magnitudes of the nonlinear wave components for various water depths were compared. It was found that the high-order wave components greatly increase as the water depth decreases. The wave kinematics at various locations were calculated and compared with the linear and the Stokes 2nd-order theories.
Characteristics of Piezoelectric Sensor for Fluid Impact Pressure
Choi, Young-Myung ; Kim, Hyun-Yi ; Park, Jun-Soo ; Kwon, Sun-Hong ; Kim, Dong-Jean ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 17~22
This study presents an investigation of the characteristics of piezoelectric sensors whose main utilization is to measure impact pressure. The piezoelectric sensors were tested from several points of view. Their characteristics were investigated for repeatability, the effect of the diameter, temperature effect, water purity, flush mounting, and AC and DC coupling. Out of these, it was revealed that the temperature effect is very significant. The characteristics of the AC and DC coupling are also very important in understanding the time history of the impact pressure.
Wave Interaction with a Porous Circular Cylinder of Non-Uniform Porosity
Cho, Il-Hyoung ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 23~31
The interaction of incident monochromatic waves with a bottom-mounted vertical porous circular cylinder is investigated using the framework of the three-dimensional linear potential theory. The porosity of the circular cylinder is uniform vertically but varies in the circumferential direction. By adjusting the porosities of the circular cylinder, both the wave blocking performance of a porous semi-circular breakwater and the wave responses inside a circular harbor with an entrance are applied as calculation examples. It is found that the reflected waves, wave run-up, and wave forces are significantly reduced due to wall porosity, which are positive factors for a breakwater, and the amplification factor of a circular harbor at resonant frequencies is greatly reduced by a porous sidewall.
Application Study on FMEA(Failure Mode and Effect Analysis) for Waterjet-lifter of Deep-Sea Manganese Nodule Miner
Choi, Jong-Su ; Hong, Sup ; Lee, Tae-Hee ; Kim, Hyung-Woo ; Yeu, Tae-Kyeong ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 32~38
An FMEA for the waterjet-lifter of a DSNM is performed to prevent the occurrence of device failure. A waterjet-lifter raises and transports manganese nodules from the deep-sea floor up to a somewhat elevated place, from which a pin-scraper transports the lifted nodules to the inner space of the DSNM. A concept design for a device using the axiomatic design methodology is shown as the mapping between the functional domain and physical domain. The FMEA for a DSNM is introduced briefly and the rating criteria of severity, occurrence, and detection for the DSNM are defined. The FMEA of the functional requirements of a DSNM device is accomplished. Three kinds of failure modes, as well as their effects and causes, are predicted. Current design control methods for detecting potential failures, such as physical or computational experiments, design confirmation, and mathematical calculation, are described and the recommended actions for several significant causes are suggested.
Preliminary Experimental Study on Biofouling in Real Sea Environment
Jung, Dong-Ho ; Kim, Ah-Ree ; Moon, Deok-Soo ; Lee, Seung-Won ; Kim, Hyeon-Ju ; Ham, Yun-Ho ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 39~43
A flow and low temperature of deep seawater the biofouling properties in a seawater environment of different materials, such as a steel pipe, polyethylene pipe, and nylon net, used for ocean industries. Experiments in a real sea environment were performed to grasp the quantitative and qualitative biofouling from diatoms attached to materials by measuring the Chlorophyll-a density. Experimental samples were placed under five types of ocean environmental conditions and analyzed every month for five months. It is shown that the biofouling by diatoms was strongly affected by the seawater temperature for all of the experimental samples. It was found that diatoms mainly adhered to the nylon net, while crustaceans prefer polyethylene, under a high temperature condition. It is believed that the biofouling properties are strongly related to the surface roughness of a material. The biofouling under the low temperature condition of deep seawater was rare and stable for the experimental periods. The inside of a pipe conveying deep seawater can be presumed to remain clear without biofouling on the condition of a flow and low temperature of deep seawater.
Dynamic Behavior of a Breasting Dolphin with Various Dolphin Heights and Slopes
Yoon, Gyeong-Seug ; Cho, Won-Chul ; Jo, Chul-Hee ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 44~52
In this study, the behavior of a breasting dolphin with various dolphin heights and formations in the coastal area of Incheon was investigated. The dynamic deflection, shear stress, and moment of the pile were analyzed using the coefficient of the horizontal subgrade reaction that resulted from loading tests of different DWT (Dead Weight Tonnage). In the case of a vertical pile type dolphin, the deflection, shear stress, and moment increased as the dolphin height increased. In the case of the battered pile type dolphin, small values of shear stress and moment were shown at a low dolphin height, and the characteristics of the dynamic behavior of the dolphin showed that the deflection, shear stress, and moment increased as the pile slope of the dolphin decreased or the DWT increased.
Motion Response and Mooring Analysis of Mobile Harbors Moored in Side-by-side
Kim, Young-Bok ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 53~60
Recently, since there are several problems in space, the infra-structure and the facilities in the contiguity of the existing harbors due to the trend of enlarging the container capacity of the large container vessel, a special floating platform named as the Mobile Harbor has been proposed conceptually as an effective solution of those problems. Two kinds of hull shapes, a conventional mono-hull type and a catamaran type, are proposed as midway feeders to transfer containers to the harbor on land from a large container ship on near shore. In this study, the motion response and mooring analysis are carried out for comparing the global performance of two types of Mobile Harbor. Robot arm mooring facility specially is devised and newly tried to use for the safe fixation of a large container ship and the Mobile Harbor on near shore. It would be expected for this comparison study to give a guideline to design the efficient hull form for a midway loader.
Study on Optimum Design of FPSO Spread Mooring System
Lim, Yu-Chang ; Kim, Kyung-Su ; Choung, Joon-Mo ; Kim, Jae-Woo ; Kim, Jin-Tae ; Yeo, Seung-Hoon ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 61~66
For a spread-moored FPSO (Floating Production, Storage, & Off-loading) subjected to environmental excitation from waves, current, and wind, a procedure to determine optimum length and stiffness of mooring lines is suggested using quasi-static frequency domain response analyses. Coupled relations between design parameters are closely examined. In consideration of this, optimized design parameters are proposed based on minimum weight condition. The initial design parameters for numerical analyses are calculated using the static catenary equation of mooring lines. It is demonstrated the line tension and vessel's offset are influenced by the mooring line length and stiffness. Accordingly it is suggested the optimum vessel's offset range should be determined considering line fatigue damage. The availability and limitation of the application of quasi-static analysis method for spread mooring system are explained by comparing the result of time domain analysis with one of frequency domain analysis.
A Study on Cutting Path Optimization Using Genetic Algorithm
Park, Ju-Yong ; Seo, Jeong-Jin ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 67~70
Nesting and cutting path optimization have a great effect on the improvement of productivity in many industries such as shipbuilding, automotive, clothing, and so on. However, few researches have been carried out for the optimization of a cutting path algorithm. This study proposed a new method for cutting optimization using gravity center of cutting pieces and a genetic algorithm. The proposed method was tested for a sample plate including many different shapes of cutting pieces and compared to 2 other conventional methods. The test results showed that the new method had the shortest cutting path and the best effectiveness among the 3 methods.
Prediction of Effective Horsepower for G/T 4 ton Class Coast Fishing Boat Using Statistical Analysis
Park, Chung-Hwan ; Shim, Sang-Mog ; Jo, Hyo-Jae ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 71~76
This paper describes a statistical analysis method for predicting a coast fishing boat's effective horsepower. The EHP estimation method for small coast fishing boats was developed, based on a statistical regression analysis of model test results in a circulating water channel. The statistical regression formula of a fishing boat's effective horsepower is determined from the regression analysis of the resistance test results for 15 actual coast fishing boats. This method was applied to the effective horsepower prediction of a G/T 4 ton class coast fishing boat. From the estimation of the effective horsepower using this regression formula and the experimental model test of the G/T 4 ton class coast fishing boat, the estimation accuracy was verified under 10 percent of the design speed. However, the effective horsepower prediction method for coast fishing boats using the regression formula will be used at the initial design and hull-form development stage.
A Study on a Dynamic Radar Cross Section Analysis Technique for a Surface Warship
Kim, Kook-Hyun ; Kim, Jin-Hyeong ; Choi, Tae-Muk ; Kim, Yun-Hwan ; Cho, Dae-Seung ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 77~81
The radar cross section (RCS) of a warship is one of the most important design features in terms of her survivability in hostile environments. Ocean waves continuously changes the attitude of an objective warship to hostile radar and distorts the RCS as a result. This paper presents a dynamic RCS analysis technique and procedure that considers temporal ship motion. First, data sets are prepared for ship motions in 6 degrees of freedom, which are numerically simulated for an objective warship via frequency to time domain conversion with response amplitude operators and specified ocean wave spectra. Second, a series of RCS analysis models are transformed geometrically by referring to ship motion data sets. Finally, temporal RCS analyses are carried out with the RCS simulation code, SYSCOS. As an example, RCS analysis results are given for a virtual warship, which show that ship motions temporally change RCS values and cause RCS reduction compared with static value in terms of mean values.
New Global Curve-Fitting Method Using Frequency Response Function
Min, Cheon-Hong ; Park, Han-Il ; Bae, Soo-Ryong ; Jeon, Jae-Jin ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 82~86
Several damping materials have been employed to reduce the vibration of structures. While it is important to estimate the damping matrix when analyzing damped composite structures using the finite element method (FEM), at present, there is no FEM program that can correctly estimate the damping matrix. In this paper, a new global curve-fitting method is proposed for identifying the system parameters of non-proportional damping structures using a frequency response function. An experimental test for a cantilever beam attached damping material was carried out to verify the performance of the method proposed in this study.
The Effect of Aging Treatment on the Corrosion Resistance in Super Duplex Stainless Steel with Added W
Kim, Soo-Chun ; Choi, Han-Gul ; Kim, Yun-Kyu ; Park, Young-Tae ; Lee, Jong-Mun ; Park, Jin-Hwan ; Kang, Chang-Yong ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 87~92
The effect of aging on the precipitation of the
phase and the corrosion resistance in tungsten substituted super duplex stainless steels was investigated. The volume fraction of the
phase and the current density increased with aging at temperatures up to
and then decreased. With an increase in aging time, the volume fraction of the
phase and the current density also increased. The
phase hardly influenced the corrosion resistance. With the substitution of tungsten for molybdenum in super duplex stainless steel, the volume fraction of the
phase and the current density decreased remarkably.
Based Composite Materials
Lee, Sang-Pill ; Cho, Kyung-Seo ; Lee, Jin-Kyung ; Bae, Dong-Su ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 93~98
The mechanical properties of
based composites containing various types of reinforcement, such as SiC,
, and W, were investigated, based on detailed examinations of their microstructures.
based composites were fabricated at a temperature of
using a hot-press device. The volume fraction of SiC and
particles in this composite system was fixed as 20%. The volume fraction of three types of W particles was changed from 10% to 30%. The characteristics of the
based composites were determined by means of optical microscopy and a three-point bending test. The addition of W particles to the
powders exhibited a sufficient improvement in the microstructure and mechanical property of the sintered
materials, compared to those of SiC and
particles. In particular, W/
composites containing W particles of 20 vol% represented a good flexural strength of about 530MPa at room temperature, accompanying a relative density of about 92%. The flexural strength of the W/
composites tended to decrease with an increase in the average size of the W particles.
A Study on the Tribological Characteristics of a Frying Pan Coated with PTFE and Nano-Diamond
Lee, Jin-Ho ; Kim, Hyun-Soo ; Yoon, Han-Ki ; Kim, Tae-Gyu ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 99~104
PTFE has good mechanical and chemical stability at a wide range of temperatures and demonstrates a low friction coefficient value. PTFE is being used for self-lubricating parts in industry. But it shows a high wear rate. Thus, PTFE and nano-diamond powder were mixed into a composite and the wear properties of a PTFE coating layer on Al6061 was investigated. A ball-on-disk type of wear tester was used under a dry condition and different temperatures of oil. After the wear test, the wear track wasexamined by optical microscope. The PTFE-diamond showed the lowest friction coefficient (0.02) of all the lubricants in the experiments. The friction coefficient was shown to be directly related to the diamond powder in the PTFE coating. Adhesion estimations were performed by a scratch test, which is mainly used for coatings. The critical load between the coating and substrate was defined through analyses of the friction load, normal load curve, and acoustic emissions, along with optical microscope observations. The scratch test results showed that an import item (SWISS) gave the highest critical load values.
Statistical Properties of Vickers Hardness of Post Weld Heat Treated Friction Welded Parts in Alloy718
Kong, Yu-Sik ; Kwon, Hyeok-Yong ; Kim, Seon-Jin ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 105~110
The objective of this paper is to investigate the statistical properties of Vickers hardness (HV) for friction welded parts in a Ni-based super alloy (Alloy718). In the case of post weld heat treatment (PWHT) parts, hardness tests were repeated for three different applied loads, 100, 200, and 300 g, with a duration time of 10 seconds. The arithmetic means of the Vickers hardness in heat affected zone (HAZ) materials were smaller than those of the base metal (BM) in all of the applied loads. The coefficient of variation (COV) for the BM and HAZ decreased by increasing the applied load. The probability distribution of the Vickers hardness followed the Weibull distribution well. The distribution of the Vickers hardness was not found to be symmetric. The shape parameter and scale parameter increased by increasing the applied load at both the BM and HAZ.
Dispertion Effect of Hydration Heat due to Materials and Standard Variation of Embedded Heat Pipe
Kim, Myung-Sik ; Yeom, Chi-Sun ; Baek, Dong-Il ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 111~116
The cracking due to hydration heat in mass concrete must be resolved to improve the stability and durability of concrete structures. In this study, the economic efficiency was improved by replacing a copper pipe with a steel one for the heat pipe, and the heat pipe was standardized to significantly improve the operation efficiency, such as the processing, transport, assembly, and construction time. As a result of the experiment, the peak temperature of the ICSHP, ISSHP, and ISUHP specimens decreased by about
compared to the OPC specimen and the probability of a thermal crack being generated in the ICSHP, ISSHP, and ISUHP specimens decreased by up to 84~88%.
Numerical Simulation of Guided Ultrasonic Waves for Inspecting Epoxy Thickness in Aluminum-Epoxy-Aluminum Adhesive Plates
Lee, Ju-Won ; Na, Won-Bae ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 117~123
This paper presents a numerical simulation of guided ultrasonic waves propagating in aluminum-epoxy-aluminum adhesive plates. In particular, this study investigated the effect of the epoxy thickness on the dispersive patterns, such as the phase velocity and group velocity of guided ultrasonic waves. In addition to investigating the dispersive curves, a numerical simulation using the pulse-echo method was carried out. This simulation showed that the degree of sensitivity of the epoxy thickness is dependent on the curvature of the phase and group dispersion curves, the maximum amplitude of the received time signals, and the peak frequency of the real components of the Fourier transform. Then, the linear relations between the epoxy thickness and the received and transformed signals were constructed to estimate the epoxy thickness.
Finite Element Simulation of Elastic Waves for Detecting Anti-symmetric Damages in Adhesively-Bonded Single Lap Joint
Woo, Jin-Ho ; Na, Won-Bae ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 124~130
This study presents a finite element simulation of elastic waves for detecting anti-symmetric damages in an adhesively-bonded single lap joint. Plane strain elements were used for modeling adherents (aluminum) and adhesives (epoxy). Three types of damage were introduced: thickness reduction, elasticity deterioration, and voids in the adhesive layers, and two excitation and reception arrangements (ER1 and ER2) were used to investigate the detectability of the damage. The simulation showed that symmetrically located damage, such as a thickness reduction, can be detected by one excitation and one reception arrangement (ER1) and anti-symmetric damages, such as elasticity deterioration and voids, can be detected by modified two-point elastic wave excitation (ER2). Compared with the ER1 arrangement, the ER2 arrangement does not require a baseline signal for damage detection; hence, an efficient method of anti-symmetric damage detection in an adhesively-bonded single lap joint is proposed.
Optimum Design of Reinforced Concrete Beam Using Genetic Algorithms
Kim, Bong-Ik ; Kwon, Jung-Hyun ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 131~135
We present an optimum design method for a rectangular reinforced concrete beam using Genetic Algorithms. The optimum design procedure in this paper employs 2 design cases: i) all of the design variables (b, d, As) of the rectangular reinforced concrete section are used pseudo-continuously, ii) one is pseudo-continuous for the concrete cross section (b, d) and the other is discrete, using an index for the steel area (As). The optimum design in this paper uses Chakrabarty's model. In this paper, the Genetic Algorithms use the method of Elitism and penalty parameters to improve the fitness in the reproduction process, which leads to very practical designs. The optimum design of the steel area in the examples uses ASTM standard reinforcing bars (#3~#11, #14, #18).
Research on Wireless Sensor Network System Design for Safety Management of Marine Structures
Han, Young-Soo ; Lee, Kyung-Ho ; Choi, Si-Young ; Kim, Chung-Hyun ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 136~145
There are two purposes for the marine structures used for fossil fuel: transporting huge amounts of crude oil and petroleum products and producing petroleum resources on the ocean in an isolated operational environment. Both types of structures are exposed to dangerous situations by sea conditions. Such marine structures are greatly affected by ocean climate conditions and its changes. Because of such ocean climate changes, it has been necessary to monitor marine structures. This research discusses the difficulties with adopting a new methodology based on a ubiquitous sensor network and develops an optimized sensor network management system design for a marine structure.
Path Tracking Control Based on RMAC in Horizontal Plane for a Torpedo-Shape AUV, ISiMi
Kim, Young-Shik ; Lee, Ji-Hong ; Kim, Jin-Ha ; Jun, Bong-Huan ; Lee, Pan-Mook ;
Journal of Ocean Engineering and Technology, volume 23, issue 6, 2009, Pages 146~155
This paper considers the path tracking problem in a horizontal plane for underactuated (or non-holonomic) autonomous underwater vehicles (AUVs). Underwater mapping has been an important mission for AUVs. Recently, underwater docking has also become a main research field of AUVs. These kinds of missions basically require accurate attitude and trajectory control performance. However, the non-holonomic problem should be solved to achieve accurate path tracking for the torpedo-type of AUVs. In this paper, resolved motion and acceleration control (RMAC) is considered as a path tracking controller for an underactuated torpedo-shaped AUV, ISiMi. A set of numerical simulations is carried out to illustrate the effectiveness of the proposed RMAC scheme, and experimental data with ISiMi100 and discussions are presented.