• Journal of Ocean Engineering and Technology
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• v.19 no.4 s.65
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• pp.49-55
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• 2005

We constructed and demonstrated a numerical CADMAS-SURF(V4.0) model that reproduces the wave run-up characteristics on the slope of coastal structures and applied it to a permeable coastal structure. We also compared the numerical model with published experimental results on the hydrodynamic phenomena of structures and some numerical results for a modified Pbreak model. In conclusion, the CADMAS-SURF model efficiently simulated wave run-up on the slope of a permeable coastal structure. The inflow/outflow effects from the porous structure boundary were approximately $15\%$ more than with the modified Pbreak model. Nevertheless, the descriptions of the internal hydraulic characteristics still could not be full!! exacted from the result(Fig. 1 참조)s obtained in our model experiment.

• The Journal of Korea Robotics Society
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• v.12 no.1
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• pp.1-10
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• 2017

For dismantling heavy structure under special environment in radioactivity, there are many problems which should be tele-operated and feedback a cutting force for cutting a thick structure such as concrete. When operator dismantles a thick heavy concrete structure, it is in sufficient to judge whether robot is contacting or not with environment by using only vision information. To overcome this problem, force feedback and impedance model based bilateral control are introduced. The sliding mode control with sliding perturbation observer (SMCSPO) based bilateral control is applied and surveyed to a single rod hydraulic cylinder in this paper. The sliding mode control is used for robustness against a disturbance. The sliding perturbation observer is used for estimation of a reaction force such as cutting force. The bilateral control is executed using the information of reaction force estimated by SMCSPO. The contribution of this paper is that the estimation method and bilateral control of the single rod hydraulic cylinder are introduced and discussed by experiment.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.4
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• pp.327-334
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• 1994

The manifold designates a pipe system discharging or absorbing water through multiple holes installed along the finite length of the pipe. The proper design of the manifold requires the pre-analysis of the hydraulic characteristics such as system head and flow rate. head loss and hole discharges, etc. On the contrary to the general pipe systems. the head loss along the pipe is hardly quantified in an explicit way since it is complicately varied by the size and arrangement of the holes. In the present study, both energy and continuity equations are employed to analyze the hydraulic characteristics, constituting nonlinear simultaneous equations which are solved by Newton method. In addition, a hydraulic experiment utilizing the manifold system equipped with an automatically controlled valve is performed to reproduce model tide. The result shows that the manifold system can be effectively used in a tidal basin where water flow should be maintained uniformly over the basin width.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.43-47
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• 2019

In this study, capability of an air slot in a siphon spillway for controlling outflow discharge is investigated through hydraulic experiments. Arc and rectangular shapes of air slot are considered and the open area of air slot can be varied. Complex air-regulated flow occurs inside the the siphon spillway when the air slot is installed on it. The same discharge is measured at the same water level inside the reservoir when the water level rises or falls. Nondimensional discharge through the siphon spillway increases slowly as nondimensional open area of the air slot increases. The hydraulic experiments show that the control of outflow discharge of siphon spillway is possible by controlling the open area of the air slot.

• Journal of Wetlands Research
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• v.18 no.4
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• pp.413-423
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• 2016

Effects of the design flood share of the Kyeongpo retarding basin, which has a function for flood control of the Kyeongpo river assigned to the Kyeongpo prickly water lily wetland, on the Kyeongpo lake and the downstream of Kyeongpo river were analyzed on the bassis of the hydraulic experiments and the numerical simulations using RMA-2 model. Reproducing a complex water flow system of the area of Kyeongpo lake, the unsteady flow simulations were performed. The data obtained in hydraulic experiments were used to determine parameters of the numerical model which simulated the flows for various flood scenarios in the downstream area of Kyeongpo river. With increasing the design flood share rates in the retarding basin, the water level was increased in the lake and is decreased in the river. The characteristics of flood flow interaction between Kyeongpo river and Kyeongpo lake were understood. These results may be used to management the Kyeongpo lake during flood season.

• Journal of Wetlands Research
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• v.19 no.4
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• pp.484-490
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• 2017

In order to examine flow characteristics according to the shape of the meandering low flow channel in the compound cross section typed straight channel, we assumed the representative channel type in Korea and confirmed the validity of the 3D numerical simulation by carrying out the hydraulic model. Based on this study, numerical simulations were also conducted on other types of river channel. As a result of the numerical model test (using the velocity value measured by the water depth observation from the hydraulic model test), it was confirmed that the numerical simulation results are in good agreement with the numerical simulation results. As a result of analyzing the flow field according to the changes in the shape of the low flow channel, it was confirmed that the secondary flow examined in the previous studies occurred. Also, it was confirmed that the maximum flow velocity point moves according to the expansion cross sectional area of flow in high flow plain. Ultimately, it is thought that it is necessary to understand the position of the water impingement (which is an important factor in river design) and the extent of the impact because the change of the channel width affects the flow.

• Journal of Drive and Control
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• v.21 no.1
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• pp.38-45
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• 2024

The power delivery is crucial to designing agricultural machinery. Therefore, the tractor-mounted potato harvester was used in this study to conduct the field experiment and analyze the power delivery for each step. This study was focused on an analysis of power delivery from the engine to the hydraulic components for the tractor-mounted harvester during potato harvesting. Finally, the simulation model of a self-propelled potato harvester was developed and validated using the experimental dataset of the tractor-mounted potato harvester. The power delivery analysis showed that approximately 90.22% of the engine power was used as traction power to drive the tractor-mounted harvester, and only 5.10% of the engine power was used for the entire hydraulic system of the tractor and operated the harvester. The statistical analysis of the simulation and experimental results showed that the coefficient of determinations (R²) ranged from 0.80 to 0.96, which indicates that the simulation model was performed with an accuracy of over 80%. The regression models were correlated linearly with the simulation and experimental results. Therefore, we believe that this study could contribute to the design methodology and performance test procedure of agricultural machinery. This basic study would be helpful in the design of a self-propelled potato harvester.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.805-817
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• 2016

This study considered the existing approximation theories of solitary wave for stable generation of it with different waveforms in a hydraulic/numerical wave tank for coping with the tsunami. Based on the approximation theory equations, two methods were proposed to estimate various waveforms of solitary wave. They estimate different waveforms and flow rates by applying waveform distribution factor and virtual depth factor with the original approximate expressions of solitary wave. Newly proposed estimation methods of solitary wave were applied in the wave generation of hydraulic/numerical wave tank. In the result, it was able to estimate the positional information signal of wave generator in the hydraulic wave tank and to find that the signal was very similar to an input signal of existing hydraulic model experiment. The waveform and velocity of solitary wave was applied to the numerical wave tank in order to generate wave, which enabled generate waveform of tsunami that was not reproduced with existing solitary wave approximation theory and found that the result had high conformity with existing experiment result. Therefore, it was able to validate and verify the two proposed estimation methods to generate stable tsunami in the hydraulic/numerical wave tank.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.1002-1012
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• 2024

To remove insoluble fission products, which could possibly cause reactor instability and significantly reduce heat transfer efficiency from primary system of molten salt reactor, a helium bubbling method is employed into a passive molten salt fast reactor. In this regard, two-phase flow behavior of molten salt and helium bubbles was investigated experimentally because the helium bubbles highly affect the circulation performance of working fluid owing to an additional drag force. As the helium flow rate is controlled, the change of key thermal-hydraulic parameters was analyzed through a two-phase experiment. Simultaneously, to assess the applicability of numerical model for the analysis of two-phase flow behavior, the numerical calculation was performed using the OpenFOAM 9.0 code. The accuracy of the numerical analysis code was evaluated by comparing it with the experimental data. Generally, numerical results showed a good agreement with the experiment. However, at the high helium injection rates, the prediction capability for void fraction of helium bubbles was relatively low. This study suggests that the multiphaseEulerFoam solver in OpenFOAM code is effective for predicting the helium bubbling but there exists a room for further improvement by incorporating the appropriate drag flux model and the population balance equation.

• Journal of Navigation and Port Research
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• v.38 no.4
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• pp.421-427
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• 2014

In order to protect coastal facilities mainly from wave and current actions, the self-locking eco blocks constituting elements of protecting shore structures against scouring were designed. These blocks are adapted to the sloping bottom, coastal dunes, and submerged coastal pipelines, counteracting the destructive and erosive impulse action. A series of laboratory experiments has been conducted to investigate the reflection of water waves over and against a train of protruded or submerged shore structures and compare the reflecting capabilities of incident waves including wave forces. In this study the hydraulic model experiment was conducted to identify the performance of newly designed water affinity eco blocks to keep the coast slope and bottom mound from scouring by reduction of the wave reflection and to convince stability of the block placement. Revised design of each block element was also tested for field conditions. From the result of experiments, the field applicability of the developed blocks and placement was discussed afterward.