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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 25, Issue 6 - Dec 2011
Volume 25, Issue 5 - Oct 2011
Volume 25, Issue 4 - Aug 2011
Volume 25, Issue 3 - Jun 2011
Volume 25, Issue 2 - Apr 2011
Volume 25, Issue 1 - Feb 2011
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Hydrodynamic Forces Characteristics of a Circular Cylinder with a Damping Plate
Cho, Il-Hyoung ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 1~7
DOI : 10.5574/KSOE.2011.25.1.001
The radiation of water waves by a heaving truncated circular cylinder with damping plate is solved in the frame of the three-dimensional linear potential theory. The damping plate has a distinct advantage in reducing the motion response of a floating circular cylinder by increasing the added mass and the damping coefficient. Using the matched eigenfunction expansion method, the characteristics of hydrodynamic added mass and the damping coefficient are investigated with various system parameters, such as the radius and submergence depth of the damping plate. It is found that both added mass and the damping coefficient are significantly increased due to the arranged features of the larger damping plate with shallow submergence, which are positive factors as a motion reduction device of the floating offshore platform. Also the numerical results for an oscillating submerged disk show that the added mass is negative and that the damping coefficient has a peak value at resonant frequency when submergence depth is sufficiently small.
Estimation of Wave Energy Extraction Efficiency for a Compact Array System of Small Buoys
Choi, Yoon-Rak ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 8~13
DOI : 10.5574/KSOE.2011.25.1.008
A compact array system of small buoys is used for wave energy extraction. To evaluate the performance of this system, hydrodynamic analysis is carried out in regular waves using the higher order boundary element method. The motion response of each buoy is calculated considering hydrodynamic interactions caused by other buoys. The effect of energy extraction device is modeled as a linear damping load. The efficiencies of energy conversion are compared using the various sizes and arrangements of the array system and the damping coefficients for energy extraction. The increase in size or the packing ratio of the system gives better efficiency. However, the wave condition and the cost for the system should be considered to optimize performance from the perspective of engineering and economics. The proposed nondimensionalized damping coefficient for energy extraction is 0.1~0.5.
A Laboratory Study for Erosional Properties of Cohesive Sediments from Mokpo Coast
Kim, Man-Kon ; Yang, Su-Hyun ; Tae, Dong-Hyeon ; Hwang, Kyu-Nam ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 14~21
DOI : 10.5574/KSOE.2011.25.1.014
The purpose of this study is to quantify the erosional parameters, such as the critical shear stress for erosion and the erosion rate coefficient for cohesive sediments from the Mokpo coast. Using Chonbuk annular flume, five erosion tests were conducted under the uniform bed condition but a different bed density respectively. Erosion test results for Mokpo sediments have shown increases in the range of
but decreases exponentially in the range of
for the given bed shear stress of
. The erosional parameters of Mokpo sediments are found to vary remarkably in quantity compared with those for cohesive sediments from other sites. On the whole, the value of Mokpo coast sediments appears to be similar to Kunsan sediments but smaller than Saemankeum and Okeechobee sediments. On the other hand, Mokpo sediments have been shown to be larger than Saemankeum and Okeechobee sediments but smaller than Kunsan sediments.
A Study of the Resistance Characteristics of Double Keel Yacht
Lee, You-Shin ; Jeong, Uh-Cheul ; Kim, Kyu-Sun ; Park, Je-Woong ; Kim, Do-Jung ; Park, Kyung-Hun ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 22~26
DOI : 10.5574/KSOE.2011.25.1.022
The resistance performances of a small leisure yacht with two different keels, center and double, respectively, are investigated using a model test at circulating water channel and CFD analysis. Flow patterns around the keels are observed using a tuft test to make clear the relation between the resistance performance and the flow characteristics around the keels. The results show that the keel does not affect free surface flows and that the double keel yacht has better performance compared to a single keel yacht in oblique condition from the resistance point of view.
The Estimation of the Propulsion Performance of a UUV Using Commercial Thruster
Lee, Chong-Moo ; Choi, Hyun-Taek ; Kim, Ki-Hun ; Yeo, Dong-Jin ; Lee, Pan-Mook ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 27~31
DOI : 10.5574/KSOE.2011.25.1.027
The previously developed method of estimating the propulsion performance of a UUV was applied to the high speed UUV, which is propelled by commercial thrusters. The thrusters were selected with an overdesign mentality; in other words, their capacities were excessive. At that point, the designer's concern was focused on a question regarding at what rpm the UUV could reach the design speed. Because the developed method required thrust coefficient curve data, the researchers asked for the POW data of the thrusters from the manufacturer. From the data, the researchers extracted the thrust coefficient and estimated the rpm value of design speed for the UUV. Finally, the researchers compared the estimated value and the result from a self-propulsion test using a VPMM (Vertical planar motion mechanism) test at a towing tank in MOERI.
Corrosion Resistance of Galvanized Steel by Treating Modified Si Organic/Inorganic Hybrid Coating Solution
Seo, Hyun-Soo ; Moon, Hee-Joon ; Kim, Jung-Ryang ; Kim, Jong-Soon ; Ahn, Seok-Hwan ; Moon, Chang-Kwon ; Nam, Ki-Woo ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 32~38
DOI : 10.5574/KSOE.2011.25.1.032
Galvanized steel has gone through a chemical process to keep it from corroding. The steel gets coated in layers of zinc because rust will not attack this protective metal. For countless outdoor, marine, or industrial applications, galvanized steel is an essential fabrication component. The reduction of the corrosion rate of zinc is an important topic. In the past, a very popular way to reduce the corrosion rate of zinc was to use chemical conversion layers based on
. However, a significant problem that has arisen is that the use of chromium salts is now restricted because of environmental protection legislation. Therefore, it is very important to develop new zinc surface treatments that are environmentally friendly to improve the corrosion resistance of zinc and adhesion with a final organic protective layer. In this study, a Urethane solution (only Urethane 20 wt.%; S-700) and an organic/inorganic solution with Si (Si polysilicate 10 wt.% + Urethane 10 wt.%; LRO-317) are used. Based on the salt spray test of 72 h, S-700 and LRO-317 had a superior effect for the corrosion resistance on EGI and HDGI, respectively.
The Study of Transmittance and Conductivity in ZnO/Ag Multilayer Films
Kim, Yun-Hae ; Kim, Do-Wan ; Murakami, Ri-Ichi ; Moon, Kyung-Man ; Lee, Sung-Yul ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 39~43
DOI : 10.5574/KSOE.2011.25.1.039
This study has lowered the specific resistance by coating a thin film layer of Ag, playing the role of the electron donor on the ZnO that is used usefully for the transparent conductive oxides. Presently, this study has examined the transmittance and electric characteristics according to the thickness of the Ag thin film layer. Also, this study has observed the transmittance and electric characteristics according to the uppermost ZnO thin film layer of ZnO/Ag/ZnO symmetric film and has conducted the theoretical investigation. In order to observe the transmittance and electric characteristics according to the thickness of the Ag thin film layer and the uppermost ZnO thin film layer, this study conducted the film deposition at room temperature while making use of the DC magnetron sputtering system. In order to see the changes in the thickness of the Ag thin film layer, this study coated a thin film while increasing by 4nm; and, in order to see the changes in the thickness of uppermost ZnO thin film layer, it performed the thin film coating by increasing by 5nm. From the experimental result, the researchers observed that the best transmittance could be obtained when the thickness of the Ag thin film layer was 8nm, but the resistance and mobility increased as the thickness got larger. On the other hand, when the thickness of the uppermost ZnO thin film layer was 20nm, the experiment yielded the best transmittance with excellent electric characteristics. Also, when compared the ZnO/Ag asymmetric film with the ZnO/Ag/ZnO symmetric film, the ZnO/Ag asymmetric film showed better transmittance and electric characteristics.
The Characteristics of Painted Coating on Aluminum Sheet by Sending Conditions
Yoon, Han-Ki ; Choi, Seok-In ; Lee, Jong-Ho ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 44~48
DOI : 10.5574/KSOE.2011.25.1.044
Researchers suggested painted coating characteristics of aluminum sheet by various sending condition. Painted coating is used to protect the surface of the blocks from the interior and exterior. It is also used to enhance the value of automobiles and ship materials. This process makes the materials surface for protection and elegance. Although analysis of the roughness and critical scratch load of painted coating is important, the effects of this material have not progressed much. In this study, the characteristics of painted coating in the other conditions of the polished aluminum sheet were investigated. The results of both various conditions and initial roughness values were almost similar to final values after painted coating.
An Experimental Study on the Material Properties of the EG/AD Model Ice Used for Ice Model Basins
Kim, Jung-Hyun ; Choi, Kyung-Sik ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 49~55
DOI : 10.5574/KSOE.2011.25.1.049
The EG/AD/S model ice, originally developed by Timco (1986), was selected as the primary model ice material for the newly built MOERI Ice Model Basin in Korea. However, the existence of a sugar component in the EG/AD/S mixture may cause a serious maintenance problem, as described in certain references. This study focuses on the tests of the mechanical properties of the EG/AD/S and the EG/AD model ice. In order to understand the influence of sugar in the original EG/AD/S model ice and to find a possible substitute for sugar, a series of tests with the EG/AD model ice were performed, and the results were compared to those of the EG/AD/S model ice. The relatively large size of the MOERI Ice Model Basin made it difficult to control the initial strength of model ice, so it took a much longer time to achieve the target strength. In order to obtain a lower strength and stiffness for the model ice, the amount of chemical additives may be varied to achieve the desired strength level. This paper is a preliminary study aimed at seeking a possible substitute for the original EG/AD/S model ice for utilization in a large-scale ice tank. To understand the influence of sugar in the original EG/AD/S model ice, the mechanical properties of the EG/AD/S and EG/AD model ice, such as flexural strength, compressive strength, and elastic modulus, were tested in the laboratory condition and compared to each other. The warm-up procedure seems to be an important factor to reduce ice strength in the tests, so it is discussed in detail.
The Influence of Treatment Condition During Low Temperature Plasma Carburizing of AISI304L Stainless Steel
Lee, In-Sup ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 56~60
DOI : 10.5574/KSOE.2011.25.1.056
A low temperature plasma carburizing process was performed to AISI 304L austenitic stainless steel to achieve the enhancement of surface hardness without a compromise in their corrosion resistance. Attempts were made to investigate the influence of the processing temperatures on the surface-hardened layer during low temperature plasma carburizng in order to obtain the optimum processing conditions. The expanded austenite (
) was formed on all the treated surfaces. Precipitates of chromium carbides were detected in the hardened layer (C-enriched layer) only for the specimen treated at
. The hardened layer thickness of
increased up to about
, with increasing treatment temperature. The surface hardness reached about 1000
, which is about 4 times higher than that of the untreated sample (250
). Minor loss in corrosion resistance was observed for the specimens treated at temperatures of
compared with untreated austenitic stainless steel. Particularly, the precipitation of chromium carbides at
led to a significant decrease in the corrosion resistance.
A Study of the FE Analysis Technique of Hybrid Blades for Large Scale Wind-Turbine
Kang, Byong-Yun ; Kim, Yun-Hae ; Kim, Do-Wan ; Kim, Myung-Hun ; Han, Jeong-Young ; Hong, Cheol-Hyun ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 61~66
DOI : 10.5574/KSOE.2011.25.1.061
According to recent figures, 35% of the world's blades are made using prepreg blades, by Vestas and Gamesa. They are the most advanced in the market today. In this study, we investigated the validity of the finite element method (FEM) applied to an FE analysis of a hybrid composite wind-turbine blade. Two methods were suggested for a composite FE analysis: using the equivalent properties of the composite or using stacking properties. FE analysis results using the stacking properties of the composite were in good agreement with results of using the equivalent properties. The difference between FE results was approximately 0.6~13.3%.
Study of the Measurement of Young's Modulus and Loss Factor for a Viscoelastic Damping Material Using a Multi Degree of Freedom Curve Fitting Method and RKU Equation
Min, Cheon-Hong ; Park, Han-Il ; Bae, Soo-Ryong ; Jeon, Jae-Jin ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 67~72
DOI : 10.5574/KSOE.2011.25.1.067
Offshore structures, such as a platform, a buoy, or a floating vessel, are exposed to several dynamic loads, and viscoelastic damping material is used to reduce the vibration of offshore structures. It is important to know the properties of viscoelastic materials because loss factor and Young's modulus of the viscoelastic damping material are dependent on frequency and temperature. In this study, an advanced technique for obtaining accurate loss factor and Young's modulus of the viscoelastic damping material is introduced based on a multi degree of freedom curve-fitting method and the RKU (Ross-Kerwin-Ungar) equations. The technique is based on a modified experimental procedure from ASTM E 756-04. Loss factor and Young's modulus of the viscoelastic damping material are measured for different temperatures by performing the test in a temperature-controlled vibration measurement room where temperature varies from 5 to 45 degrees Celsius.
A Study of the Basic Properties of Lightweight Aggregate Concrete for Offshore Structures Application
Kim, Myung-Sik ; Jang, Hee-Suk ; Kim, Chung-Ho ; Baek, Dong-Il ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 73~79
DOI : 10.5574/KSOE.2011.25.1.073
The various properties of concrete have been required, as civil engineering structures are getting larger and complicated. Therefore, the high performance of concrete, such as high strength, high fluidity, and low hydration heat, has been investigated largely. In this study, the properties of lightweight concrete-reducing self-weight of structure member have been studied in order to check the applicability of lightweight aggregate concrete to structural material. The experiments on compressive strength, splitting tensile strength, unit weight, and modulus of elasticity have been conducted with varying PLC, LWCI, LWCII, LWCII-SF5, LWCII-SF15 to check the basic properties. The compressive strength of 21MPa was obtained easily by using lightweight aggregate concrete and the addition of silica fume to increase the compressive strength slightly. To use lightweight aggregate concrete for civil engineering structures, systematic and rigorous studies are necessary.
Performance Analysis of Closed-type OTEC Cycle using Waste Heat
Lee, Ho-Saeng ; Jung, Dong-Ho ; Hong, Seok-Won ; Kim, Hyeon-Ju ;
Journal of Ocean Engineering and Technology, volume 25, issue 1, 2011, Pages 80~84
DOI : 10.5574/KSOE.2011.25.1.080
The cycle performance of closed ocean thermal energy conversion (OTEC) system with 50 kW gross power was evaluated to obtain the basic data for the optimal design of OTEC using waste heat such as solar power, discharged heat from condenser of power plant. The basic thermodynamic model for OTEC is Rankine cycle, and the surface seawater and deep seawater were used for the heat source of evaporator and condenser, respectively. The cycle performance such as efficiency, heat exchanger capacity, etc. was analyzed on the variation of temperature increase by waste heat. The cycle efficiency increased and necessary capacity of evaporator and condenser decreased under 50kW gross power with respect to the temperature increase of working fluid. Also, when the temperature increase is about
, the heat which can be used is generated. By generator with 0.9 effectiveness under the simulated condition, the cycle efficiency was improved approximately 3.0% comparing with the basic cycle.