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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 1, Issue 4 - Dec 2011
Volume 1, Issue 3 - Sep 2011
Volume 1, Issue 2 - Jun 2011
Volume 1, Issue 1 - Mar 2011
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The Processing and Mechanical Performance of Cellulose Nanofiber-based Composites
Nakagaito, Antonio Norio ; Takagi, Hitoshi ; Pandey, Jitendra Kumar ;
International Journal of Ocean System Engineering, volume 1, issue 4, 2011, Pages 180~184
DOI : 10.5574/IJOSE.2011.1.4.180
Nanocomposites based on cellulose nanofibers have been studied for a considerable time since its first introduction, however real applications seem to have hardly developed to these days. The high-strength of cellulose nanofibers suggests the potential to reinforce plastics to produce composites for semi-structural or even structural applications. This paper discusses some of the attempts to produce such high-strength nanocomposites and the main challenges that have to be overcome to bring them into commercial products.
The Research of Beach Deformation after Construction of the Jetties
Park, Sang-Kil ; Han, Chong-Soo ; Roh, Tae-Young ; Park, O-Young ; Ahn, Ik-Seong ; Lee, Ji-Hun ;
International Journal of Ocean System Engineering, volume 1, issue 4, 2011, Pages 185~191
DOI : 10.5574/IJOSE.2011.1.4.185
This research was described the prevention of coastal topographical change and sediment diffusive concentration incoming from small estuary after construction jetties. This structure is constructed to decrease sediment deposition incoming from the upstream river due to the urbanization and industrial development and to minimize effects on the coastal ecosystem. The physical modeling and numerical modeling for waves were conducted to analyze the configuration of Imrang sand beach deformation without and with construction of jetty. The specification of the installed jetty, which is able to control sedimentation concentration was decided based on the prediction of the Imrang beach area changes by space and time. As a result, the jetties constructed in the estuary retarded the rate of sand sediment, so that the effect area of sand sedimentation was obviously decreased. In addition, the measured field data indicated that the sediment deposition inside of dikes could be controlled and the right side area of jetties could be preserved without sediment deposition.
Design, Implementation and Navigation Test of Manta-type Unmanned Underwater Vehicle
Kim, Joon-Young ; Ko, Sung-Hyub ; Cho, So-Hyung ; Lee, Seung-Keon ; Sohn, Kyoung-Ho ;
International Journal of Ocean System Engineering, volume 1, issue 4, 2011, Pages 192~197
DOI : 10.5574/IJOSE.2011.1.4.192
This paper describes the mathematical modeling, control algorithm, system design, hardware implementation and experimental test of a Manta-type Unmanned Underwater Vehicle (MUUV). The vehicle has one thruster for longitudinal propulsion, one rudder for heading angle control and two elevators for depth control. It is equipped with a pressure sensor for measuring water depth and Doppler Velocity Log for measuring position and angle. The vehicle is controlled by an on-board PC, which runs with the Windows XP operating system. The dynamic model of 6DOF is derived including the hydrodynamic forces and moments acting on the vehicle, while the hydrodynamic coefficients related to the forces and moments are obtained from experiments or estimated numerically. We also utilized the values obtained from PMM (Planar Motion Mechanism) tests found in the previous publications for numerical simulations. Various controllers such as PID, Sliding mode, Fuzzy and
are designed for depth and heading angle control in order to compare the performance of each controller based on simulation. In addition, experimental tests are carried out in a towing tank for depth keeping and heading angle tracking.
Hydrodynamic Interaction Analysis of Floating Multi-body System
Kim, Young-Bok ; Kim, Moo-Hyun ; Kim, Yong-Yook ; Kim, Young-Hun ;
International Journal of Ocean System Engineering, volume 1, issue 4, 2011, Pages 198~204
DOI : 10.5574/IJOSE.2011.1.4.198
Recently, several problems have occurred in the space, infra-structure, and facility of the contiguity of existing harbors due to the trend of enlarged container vessels. In this regard, the Mobile Harbor has been proposed conceptually in this study as an effective solution for these problems. The concept is that of a transfer loader that transfers containers from a large container ship to the harbor on land, and is a catamaran type floating barge. The catamaran-type vessel is well known for its advantage in maneuverability, resistance, and effectiveness for working on board. For the safe and effective operation of the two floating bodies (a container ship and the mobile harbor in the near sea detached from the quay), robot arms, novel crane systems, and pneumatic fenders are specially devised with an additional mooring facility or DP (dynamic positioning) system. In this study, this concept is to be verified through comparison and simulation studies under various environmental conditions. It is shown that the proposed concept is in general feasible but there are several areas for further investigation and improvement.
Analysis of PLL Phase Noise Effect for High Data-rate Underwater Communications
Lee, Chong-Hyun ; Bae, Jin-Ho ; Hwang, Chang-Ku ; Lee, Seung-Wook ; Shin, Jung-Chae ;
International Journal of Ocean System Engineering, volume 1, issue 4, 2011, Pages 205~210
DOI : 10.5574/IJOSE.2011.1.4.205
High data-rate underwater communications is demanded. This demand imposes stringent requirements on underwater communication equipment of phase-locked-loop (PLL). Phase noise in PLL is unwanted and unavoidable. In this paper, we investigate the PLL phase noise effect on high order QAM for underwater communication systems. The phase noise model using power spectral density is adopted for performance evaluation. The phase noise components considered in PLL are reference oscillator, voltage controlled oscillator (VCO), filter and divider. The filters in PLL noise are assumed to be second order active and passive low pass filters. Through simulation, we analyze the phase noise characteristics of the four components and then investigate the performance improvement factor of each component. Consequently, we derive specifications of VCO, phase detector, divider to meet performance requirement of high data-rate communication using QAM under phase noise influence.
Causal Analysis of a Tugboat Capsizing Accident in Rough Weather Condition Based on a Dynamical Simulation
Yoon, Hyeon-Kyu ; Kim, Sun-Young ; Lee, Gyeong-Joong ;
International Journal of Ocean System Engineering, volume 1, issue 4, 2011, Pages 211~221
DOI : 10.5574/IJOSE.2011.1.4.211
Tugboats are widely used near harbors to assist with various operations such as the berthing and deberthing of very large vessels and the towing of barges. Capsizing accidents involving tugboats occasionally take place when the tugboat makes rapid turns in harsh weather conditions. When there is little evidence suggesting how the accident occurred and when the crew members are missing, it is necessary to predict the time history of the towing vessel’s attitude and trajectory from its departure point to when and where it capsized, depending on various input parameters using a numerical simulation. In this paper, the dynamics of a tugboat and a towed barge in conjunction with the external force and moment were established, and the possible input parameters and operational scenarios which might influence the large roll motion of the tugboat were identified. As a result of analyzing the simulated time history of the excessive roll motion of the tugboat, it was found that roll motion can take place when the tugboat is situated on the crest of a wave and when it is pulled by a towed barge through a towing line. The main cause of the accident would be the parameters that primarily influence such situations. These are the wave parameters, course changing scenario, and the amount of tension.
Approximated Generalized Torques by the Hydrodynamic Forces Acting on Legs of an Underwater Walking Robot
Jun, Bong-Huan ; Shim, Hyung-Won ; Lee, Pan-Mook ;
International Journal of Ocean System Engineering, volume 1, issue 4, 2011, Pages 222~229
DOI : 10.5574/IJOSE.2011.1.4.222
In this paper, we present the concept and main mission of the Crabster, an underwater walking robot. The main focus is on the modeling of drag and lift forces on the legs of the robot, which comprise the main difference in dynamic characteristics between on-land and underwater robots. Drag and lift forces acting on the underwater link are described as a function of the relative velocity of the link with respect to the fluid using the strip theory. Using the translational velocity of the link as the rotational velocity of the joint, we describe the drag force as a function of joint variables. Generalized drag torque is successfully derived from the drag force as a function of generalized variables and its first derivative, even though the arm has a roll joint and twist angles between the joints. To verify the proposed model, we conducted drag torque simulations using a simple Selective Compliant Articulated Robot Arm.
Damping Effect of Reinforced Polyurethane Foam under Various Temperatures
Lee, Tak-Kee ; Kim, Myung-Hyun ; Rim, Chae-Whan ; Chun, Min-Sung ; Suh, Yong-Suk ;
International Journal of Ocean System Engineering, volume 1, issue 4, 2011, Pages 230~235
DOI : 10.5574/IJOSE.2011.1.4.230
Reinforced polyurethane foam (RPUF) is one of the important materials of Mark III type insulation systems used in liquefied natural gas (LNG) cargo containment systems. However, RPUF is the most difficult material to use with regard to its safety assessment, because there is little public and reliable data on its mechanical properties, and even some public data show relatively large differences. In this study, to investigate the structural response of the system under compressive loads such as sloshing action, time-dependent characteristics of RPUF were examined. A series of compressive load tests of the insulation system including RPUF under various temperature conditions was carried out using specimens with rectangular section. As a result, the relationship between deformation of RPUF and time is linear and dependent on the loading rate, so the concept of strain rate could be applied to the analysis of the insulation system. Also, we found that the spring constant tends to converge to a value as the loading rate increases and that the convergence level is dependent on temperature.