• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.3
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• pp.181-190
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• 2010

In case of constructing submerged breakwaters, the circulation current is occurred around the open inlet because of mean water level difference between front and rear sides of them. The aim of this study is to investigate the flow control structure of new-type submerged breakwater which is able to reduce mean water level at rear side of it. At first, the numerical model (LES-WASS-3D) is validated by comparing with existing experimental data. And then, numerical simulation is carried out to examine wave height, mean water level and mean flow around the newtype submerged breakwater. From the numerical results, it can be pointed out that the new-type submerged breakwater with drainage system reduces the rip current around the open inlet.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.347-350
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• 2006

Maritime and Ocean Engineering Research Institute (MOERI), a branch of KORDI, has designed and manufactured a model of an autonomous underwater vehicle (AUV) named ISiMI(Integrated Submergible for Intelligent Mission Implementation). ISiMI is an AUV platform to satisfy the various needs of experimental test required for development of challenging technologies newly investigated in the field of underwater robot; control and navigational algorithms and software architectures. The main design goal of ISiMI AUV is downsizing which will reduce substantially the operating cost compared to other vehicles previously developed in KORDI such as VORAM or DUSAUV. As a result of design and manufacturing process, ISiMI is implemented to be 1.2m in length, 0.17m in diameter and weigh 20 kg in air. A series of tank test is conducted to verify the basic functions of ISiMI in the Ocean Engineering Basin of MOERI, which includes manual control with R/F link, auto depth, auto heading control and a final approach control for underwater docking. This paper describes the implementation of ISiMI system and the experimental results to verify the function of ISiMi as a test-bed AUV platform.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.6
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• pp.1037-1048
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• 2016

In this study, nonlinear wave interaction in the presence of a uniform current is studied using numerical model, named CADMAS-SURF which is based on the Navier-Stokes equations coupled with Volume of Fluid for tracking free surface deformation. The original CADMAS-SURF developed for interaction of wave with structure is modified/extended to simulate nonlinear fluid dynamic motions within wave-current coexisting field. The capability of Numerical Wave-Current Tank (NWCT) in this study is validated by comparing with available existing laboratory experiments for both wave-following and wave-opposing current. The numerical results for interaction between wave and current are shown to be in good agreement with experimental data. Then, this study focused on the dynamic motions of the water velocity, surface elevation and vorticity within combined wave-current field in demonstrating complex nonlinear physical phenomena due to interaction between wave and current. In addition, NWCT is applied to simulate a more complex wave-current-structure field for wave propagating over a submerged breakwater associated with current. Detailed discussion including characteristics of velocity and vorticity fields and the relation between free surface and vorticity are given.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.2
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• pp.178-185
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• 2011

In this paper, we propose the position estimation algorithm based on the multisensor fusion using equalization of state variables and feedback structure. First, the state variables measured from INS of main sensor with large error and DVL of assistance sensor with small error are measured before prediction phase. Next, the equalized state variables are entered to each filter and fused the enhanced state variables for prediction and update phases. Finally, the fused state variables are returned to the main sensor for improving the position estimation of UUV. For evaluation, we create the moving course of UUV by simulation and confirm the performance of position estimation by applying the proposed algorithm. The evaluation results show that the proposed algorithm is the best for position estimation and also possible for robust position estimation at the change period of moving courses.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.2
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• pp.105-110
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• 2019

People sleep about one-third of their lives and their sleep time varies according to age. Adult usually sleep 8 hours a day. However, that dose not guarantee good sleep. The cause of this is due to sleep disorders like snoring and sleep apnea. In this paper, the smart pillow for detecting snoring among sleep disorders is investigated. This pillow consists of two microphones located on the left and right side of the pillow. For simple detecting, the snoring signal was converted into the pulse using a peak detection circuit. The decision of the snoring occurrence was by pulse duration. The accuracy of the snoring detection was about 97%. The research results show that the smart pillow can be use to detect the snoring during sleeping.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.1 s.24
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• pp.67-72
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• 2007

A model for predicting potentials of land erosion and deposition over a natural basin was developed based on the mass balance principle. The program was developed based on sediment mass balance principle for each cell in a GIS. Sediment yield from a cell was estimated with RUSLE. The outflow sediment from a cell was calculated by multiplying the sediment yield of the cell by the sediment delivery ratio (SDR) of the cell. The outflow sediment from the upstream cell becomes the incoming sediment of the downstream cell. Therefore the erosion and deposition potential of each cell could be determined from the sediment mass balance i.e., the difference between the incoming and outflow of sediments of each cell. The developed model was validated by comparing the predicted sediment yields for three basins with measured data.

• Journal of Ginseng Research
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• v.11 no.2
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• pp.111-117
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• 1987

The phase and times on the development of dormancy bud in seedling, and those of flower organs in 2-year-old ginseng are different to those of over 2-,3-year-old plant, respectively. The growing aspects of dormancy bud in seedling were investigated from rooting stage (April, 8) to Mid-June, and those of flower organs in 2-year-old plant had done once in two days late in April after compound leaves were unfolded. Firstly, the formation of dormancy bud in seedling was begun on Mid-late in March. This is early about one month compare with those of over 2-year-old plant. Fine bud in seedling was formed between cotyledons, at W spot under young shoot. Secondly, development of flower organs in 2-year-old plant was completed from late of April to early of May after compound leaves of transplanted plant were unfolded. In tare, this is very different characteristics because plants of any other ages form the flower organs one year ago. Thirdly, flower organs of ginseng plant, over 3-year-old plant, always develop in the rhizome formed one year ago, but those of 2-year-old plant develop in apical shoot meristem.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.3
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• pp.70-76
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• 2007

Hemire is a 6000m class deep-sea ROV, which is recently developed by Maritime & Ocean Engineering Research Institute (MOERI) of Korea Ocean Research & Development Institute (KORDI) for 6 years since 2001, sponsored by the Ministry of Maritime Affairs and Fisheries (MOMAF). Hemire dove upto 1,065m for the first east sea trial last April, and touched a 2,026m bottom of the east sea last September. Finally, last November, Hemire reached a 5,775m bottom of the pacific ocean successfully. This showed our own technologies for design and development of a deep-sea ROV as 4th nation in the world, and we made a great step forward for deep-sea exploration. This paper describes a general overview of a 6000m class deep-sea ROV, and briefly explains development procedure of Hemire and Henuvy. Finally, results of sea trial are summarized.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.2
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• pp.170-178
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• 2017

This paper proposes an improved path-planning technique based on the $A^*$ algorithm. The conventional $A^*$ algorithm only considers the optimality of the planned path and sometimes produces a path that an unmanned underwater vehicle (UUV) cannot navigate due to its dynamic constraint such as the limit of the radius of gyration. It is because that the previous method evaluate the moving cost based on the straight distance between nodes. We enhance the conventional method by evaluating the moving cost on the basis of the practically navigable trajectory, which is generated by the waypoint-tracking control of the UUV dynamics. The simulation examples indeed show the effectiveness of the proposed technique.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.141-148
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• 2003

This paper presents a rotating ann test for assessment of an underwater hybrid navigation system for a semi-autonomous underwater vehicle. The navigation system consists of an inertial measurement unit (IMU), an ultra-short baseline (USBL) acoustic navigation sensor and a doppler velocity log (DVL) accompanying a magnetic compass. The errors of inertial measurement units increase with time due to the bias errors of gyros and accelerometers. A navigational system model is derived to include the error model of the USBL acoustic navigation sensor and the scale effect and bias errors of the DVL, of which the state equation composed of the navigation states and sensor parameters is 25 in the order. The conventional extended Kalman filter was used to propagate the error covariance, update the measurement errors and correct the state equation when the measurements are available. The rotating ann tests are conducted in the Ocean Engineering Basin of KRISO, KORDI to generate circular motion in laboratory, where the USBL system was absent in the basin. The hybrid underwater navigation system shows good tracking performance against the circular planar motion. Additionally this paper checked the effects of the sampling ratio of the navigation system and the possibility of the dead reckoning with the DVL and the magnetic compass to estimate the position of the vehicle.