• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.3
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• pp.261-263
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• 2023

Recently, universities of fisheries and institutions related to fisheries are actively carrying out a project to build new fisheries training ships. These new fisheries training ships are significantly larger in size and longer in length than the previous ships. In addition, these new ships basically have space that can accommodate more than 100 crew and passenger. On the other hand, they are excluded from IMO maneuverability evaluation since the size of these ships are still less than 100 m in length (LBP). These results have had an impact on the study of maneuverability of fishing vessels including the fisheries training ships. Against these backgrounds, the authors conducted a study to estimate the maneuvering characteristics of fisheries training ship Baek-Kyung according to depth in order to prepare a maneuvering characteristic index that enables the large fisheries training ships to navigate more safely using a modified empirical formula. It was confirmed that the maneuvering characteristics of Baek-Kyung changed significantly as the values of the hydrodynamic force coefficients changed as the water depth gradually decreased from around 1.5 (approx. 8 m in depth) of the ratio of the water depth to the ship draft. The results of this study will not only help navigators understand the maneuvering characteristics of Baek-Kyung, but also serve as an indicator when navigating in shallow water. In addition, the accumulation of these results will serve as a basis for future study on maneuverability of fishing vessel types.

• Journal of Korea Water Resources Association
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• v.45 no.3
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• pp.331-347
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• 2012

The downstream of the Nam River Dam is crucial region for long-term water resource planning for Busan and Gyeongnam Province. Thus, the analysis of flow behavior and water quality is necessary for the sustainable surface water management and the control of pollutant source. In this study, the flow field and BOD transport at the downstream of Nam River Dam were analyzed by incorporating 2-D water quality model, RAM4 and 3-D water quality model, WASP with the hydrodynamic model, RAM2 and EFDC, respectively. The application of 2-D flow analysis model, RAM2 showed that velocity distributions at the five transverse sections of the meandering part closely followed the measured values by ADCP, and the flow field and overflow characteristic at the submerged weir showed satisfactory performance compared with the result of 3-D EFDC model. In addition, the BOD concentration field obtained by RAM2-RAM4 coupled modeling was in good agreement with the result by EFDC-WASP model throughout the computational domain. The hydrodynamic characteristic and water quality at the downstream reach of Nam River Dam are mainly influenced by the Dam discharge, and the water quantity is closely related to the water quality control and fishery environment at the lower part of Nakdong River. Therefore, when further quantitative analysis is necessary regarding these issues, 2-D semi-coupled modeling is recommended in terms of computational effectiveness and model application aspect.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.135-142
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• 2015

Floating offshore structures should be designed by considering the most extreme environmental loadings which may be encountered in their design life. The most severe loading on a wave-offshore wind hybrid power generation system is wave loads. The principal parameters of wave loads are wave length, wave height and wave direction. The wave loads have different effects on the structural behavior characteristic depending on the combination of wave parameters. Therefore, the process of investigation for critical loads based on the individual wave loading parameter is need. Namely, the equivalent design wave should be derived by finding the wave condition which generates the maximum stress in entire wave conditions. Through a series of analysis, an equivalent regular wave height can be obtained which generates the same amount of the hydrodynamic loads as calculated in the response analysis. The aim of this study is the determination of equivalent design wave regarding to characteristic global hydrodynamic responses for wave-offshore wind hybrid power generation system. It will be utilized in the global structural response analysis subjected to selected design waves and this study also includes an application of global structural analysis.

• Journal of Korea Water Resources Association
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• v.39 no.7 s.168
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• pp.553-562
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• 2006

The relative contributions of overland-flow and stream-flow to the response process at the basin scale are evaluated in the present study. The moments of GIUH models were applied to the data of the Bocheong watershed in the Geum river basin in Korea in order to discuss the feasibility. The GIUH model derived in this study consists of the stream path and overland region. The characteristic velocities for the flows between two cases mentioned above make a clear distinction as expected and would have more physical meaning than the ones of the model by Rodriguez-Iturbe and Valdes(1979). The path lengths of overland for each stream order are nearly constant, whereas the case of stream is shown to grow larger according to the basin sizes. As a result, the overall basin response process was founded out to be greatly under the influence of the hydrodynamic behavior of overland, and its behavior is suggested to be further researched for catching the broader meanings.

• Structural Engineering and Mechanics
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• v.81 no.6
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• pp.691-703
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• 2022

To obtain the seismic response of lead-cored rubber, shape memory alloy (SMA)-rubber isolation Plate-shell Integrated Concrete Liquid-Storage Structure (PSICLSS), based on a PSICLSS in a water treatment plant, built a scale experimental model, and a shaking table test was conducted. Discussed the seismic responses of rubber isolation, SMA-rubber isolation PSICLSS. Combined with numerical model analysis, the vibration characteristics of rubber isolation PSICLSS are studied. The results showed that the acceleration, liquid sloshing height, hydrodynamic pressure of rubber and SMA-rubber isolation PSICLSS are amplified when the frequency of seismic excitation is close to the main frequency of the isolation PSICLSS. The earthquake causes a significant leakage of liquid, at the same time, the external liquid sloshing height is significantly higher than internal liquid sloshing height. Numerical analysis showed that the low-frequency acceleration excitation causes a more significant dynamic response of PSICLSS. The sinusoidal excitation with first-order sloshing frequency of internal liquid causes a more significant sloshing height of the internal liquid, but has little effect on the structural principal stresses. The sinusoidal excitation with first-order sloshing frequency of external liquid causes the most enormous structural principal stress, and a more significant external liquid sloshing height. In particular, the principal stress of PSICLSSS with long isolation period will be significantly enlarged. Therefore, the stiffness of the isolation layer should be properly adjusted in the design of rubber and SMA-rubber isolation PSICLSS.

• 한국해양학회지
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• v.18 no.2
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• pp.125-141
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• 1983

Micropaleontological analyses of the bathic foraminifera of 132 subtidal surface samples of Asan Bay located in the middle of the western coast of Korea, fringing the Yellow Sea collected during late May-early June 1982, shows the results as follows; -Forainiferal numbers of total assemblages are influenced by hydrodynamic and ecologic factors as well as by the sedimentation in the study area. -Badly preserved faunas including replaced faunas seemed to be fossils, all having living counterparts in the study area and showing a somewhat similar type of wall structures with those of the total assemblages and showing no characteristic bathymetric occurrence compared to that of the biocoenose s.1. of the species, lead to infer theirprobable derivation from the environment without a remarkable environmental difference from the study area. But this inference demands further study in consideration of the physical conditions of the study area. -Living/total ratios show a strong negative correlation with the total foraminiferal numbers excluding replaced faunas. But this trend is somewhat deviated in the relatively high ratios. -Fisher-alpha diversity indices of the total assemblages excluding replaced faunas are lying between 1.7 and 3.7. Totals assemblages are mainly composed of hyaline forms with limited porcelaneous and agglutinated ones.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.644-653
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• 1991

A wave instability problem is formulated for natural convection flows adjacent to a inclined isothermal surface in pure water near the density extremum. It accounts for the nonparallelism of the basic flow and temperature fields. Numerical solutions of the hydrodynamic stability equations constitute a two-point boundary value problem which are accurately solved using a computer code COLSYS. Neutral stability results for Prandtl number of 11.6 are obtained for various angles of inclination of a surface in the range from-10 to 30 deg. The neutral stability curves are systematically shifted toward modified Grashof number G=0 as one proceeds from downward-facing inclined plate(.gamma.<0.deg.) to upward-facing inclined plate (.gamma.>0.deg.). Namely, an increase in the positive angle of inclination always cause the flows to be significantly more unstable. The present results are compared with the results for the parallel flow model. The nonparallel flow model has, in general, a higher critical Grashof number than does the parallel flow model. But the neutral stability curves retain their characteristic shapes.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2365-2377
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• 2017

This paper addresses two interrelated problems concerning the tracking control of pod propulsion unmanned surface vessel (USV), namely, the modeling of pod propulsion USV, and tracking controller design. First, based on MMG modeling theory, the model of pod propulsion USV is derived. Furthermore, a practical adaptive neural tracking controller is proposed by backstepping technique, neural network approximation and adaptive method. Meanwhile, unlike some existing tracking methods for surface vessel whose control algorithms suffer from "explosion of complexity", a novel neural shunting model is introduced to solve the problem. Using a Lyapunov functional, it is proven that all error signals in the system are uniformly ultimately bounded. The advantages of the paper are that first, the underactuated characteristic of pod propulsion USV is proved; second, the neural shunting model is used to solve the problem of "explosion of complexity", and this is a combination of knowledge in the field of biology and engineering; third, the developed controller is able to capture the uncertainties without the exact information of hydrodynamic damping structure and the sea disturbances. Numerical examples have been given to illustrate the performance and effectiveness of the proposed scheme.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.4
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• pp.266-274
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• 2016

Many researchers have been trying to improve the propulsion efficiency of a propeller. In this study, the numerical analysis is carried out for the POW(Propeller Open Water test) performance of a propeller equipped with an energy saving device called PHVC(Propeller Hub Vortex Control). PHVC is aimed to control the propeller hub vortex behind the propeller so that the rotational kinetic energy loss can be reduced. The unsteady Reynolds Averaged Navier-Stokes(URANS) equations are assumed as the governing flow equations and are solved by using a commercial CFD(Computational Fluid Dynamics) software, where SST k-ω model is selected for turbulence closure. The computed characteristic values, thrust, torque and propulsion efficiency coefficients for the target propeller with and without PHVC and the local flows in the propeller wake region are validated by the model test results of KRISO LCT(Large Cavitation Tunnel). It is concluded from the present numerical results that CFD can be a good promising method in the assessment of the hydrodynamic performance of PHVC in the design stage.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.1
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• pp.78-84
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• 2013

The primary objective of the current work is to develop efficient numerical code to assess the resistance performance of the twin hull form. Resistance performance for the two different twin hull forms with asymmetric and symmetric mono hull using developed code are evaluated. Numerical calculations and model tests have been compared to validate a developed code used in the current work. Comparison were carried out through sinkages of the bow and stern, trim angle and wave-making resistance. Comparative analysis regarding hydrodynamic characteristic of different twin hull forms is worthy of application in the hull form development stage.