• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.3
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• pp.405-412
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• 2023

With the development of drone and ICT convergence technology, the use of underwater drones such as leisure underwater drones such as underwater exploration for fishing and industrial drones such as bridge piers is increasing. Existing motor controllers are suitable for aerial drones and these can increase the completeness of underwater drones and their reliability in motor control by developing BLDC motor controllers dedicated to underwater drones. By developing a battery management system (BMS) exclusively for underwater drones, battery stability was ensured by checking the state of charge, checking the state of discharge, adjusting cell balancing, and implementing high/voltage protection functions.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.23 no.4
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• pp.401-408
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• 2005

Presently many constructions establish in underwater, but approaching to underwater constructions are difficult, for comparing with ground, underwater environment is different in media. Usually measurement methods for underwater constructions are using tapes, using depth gauges, using acoustic positioning systems. But, tapes are hard to measure the correct distance, for applying a right tension is not easy in underwater. Depth gauges have a weakness in settling, for it takes long time to do it. Acoustic positioning systems don't work well in confined spaces and cost a lot. Hence, the purpose of this study is, at first, to understand rays path in multimedia like water, glass and air. The second thing is to perform a camera calibration at the field to compare with the interior orientation parameter. And the third thing is to find out whether photogrammetry is applied for underwater object in using cube for accuracy examination. The last thing is to perform underwater photogrammetry about underwater object, which is pier model and riverbed. We came to the conclusion through this experiment that the applying underwater photogrammerty for underwater constructions and underwater ground is possible.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.330-335
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• 2017

This study applied SONAR(Sound Navigation And Ranging) to the inspection and evaluation of underwater structures. Anactual river bridge was chosen for inspection and evaluation. SONAR and an optical camera were operated together to analyze the underwater image of the bridge. SONAR images were obtained by various methods to remove the environmental variables from the field experiment, and it was confirmed that the reliability of detecting damaged areas on piers was decreased when using SONAR alone. The SONAR equipment and the optical camera can be used simultaneously to overcome the limitations of SONAR in inspecting underwater structures.These results can be used as basic data for the development of similar technologies for underwater structure inspection.

• Journal of the Korea Society for Simulation
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• v.25 no.3
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• pp.15-28
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• 2016

It is necessary to analyze underwater acoustics channel(UAC) modeling and simulation for underwater weapon system development and acquisition. In order to analyze UAC, there are underwater acoustics propagation numerical analysis models(Ray theory, Parabolic equation, Normal-mode, Wavenumber integration). However, If these models are used for multiple frequency signal analysis, they are inaccurate to calculate result of analysis effectiveness and restricted for signal processing and analysis. In this paper, to overcome this problem, we propose simple/multiple frequency signal analysis model of the Pseudospectral Time-Domain Method synthetic environment UAC applied to underwater environment noise model as like as realistic underwater environment. In order to confirm the validation of the model, we performed the 9 scenarios simulation(4 scenarios of single frequency signal, 4 scenarios of multiple frequency signal, 1 scenario of single/multiple frequency signal like submarine radiated noise) for validation and confirmed the validation of this model through the simulation model.

• Journal of Convergence for Information Technology
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• v.9 no.6
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• pp.7-12
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• 2019

In order to shoot underwater, the photographer must be equipped with shooting equipment and enter into the water. Since the photographer directly enters the water, safety accidents occur frequently due to various obstacles or deep water in the water. The proposed underwater stereo photography technique can solve the safety accident problem caused by the entry of the photographer into the water by using the drone for underwater photographing. In addition, this technique has the advantage of obtaining underwater images at low cost. In this study, the angle of the proposed cam for stereoscopic photography was analyzed and the condition that the proper stereoscopic image can be viewed was defined as the distance from the floor of 18cm to the floor distance of 41.4cm. This provision is proposed to be used to adjust the height of the shooting area descended by the elevation chain of the water surface hovering drones.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.4
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• pp.443-450
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• 2014

In this study, we have discussed about the effect of hydrofoil arrangement and longitudinal moment characteristic on longitudinal motion stability of fully-submerged hydrofoil by the experiment of tandem hydrofoil model. First of all, tandem hydrofoil model that has canard wing arrangement has been made and characteristics of lift force and drag force by performing the lift force and drag force measuring experiment has also been estimated. Besides, tandem hydrofoil model's wing arrangement which has the initial stability and self stability of longitudinal motion has also been determined. In longitudinal stability experiment of tandem hydrofoil model, the motion characteristic of pitch and heave and the longitudinal stability of foil borne condition by variation of self stability of longitudinal moment and longitudinal distance are estimated. The result from the experiment and it's important conclusion can be described as below; Increase the self stability for longitudinal moment, the higher self stability for pitch motions in a constant pitch angles. By increasing the self stability for longitudinal moment, the range of fluctuation of pitch motion and heave motion for pitch angle also will change relatively small and longitudinal stability is excellent. Lastly, when the lift force of hydrofoil is remain constants, we can conclude that securing the enough self stability for longitudinal moment is essential for stable foil borne condition of tandem hydrofoil.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.10a
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• pp.48-49
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• 2000

잠수기 어업 등과 같은 수중 활동에서 대부분의 경우 수중과 수상 간에는 통신수단이 없거나 있어도 효율이 낮은 유선 전화기나 밧줄 등으로 의사 전달을 하고 있는 실정이다. 이에 작업의 효율성과 안전성 향상을 위하여 우리 해양 환경에 맞는 무선수중전화기 개발의 기술 자료로 활용하고자 본 연구를 수행하였다. (중략)

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.12
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• pp.1328-1336
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• 2012

Compared to terrestrial RF communications, underwater acoustic communications have several limitations such as limited bandwidth, high level of fading effects, and a large underwater propagation delay. In this paper, in order to tackle those limitations of underwater communications and to make it possible to form a large underwater monitoring systems, we propose a hierarchical underwater network architecture, which consists of underwater sensors, clusterheads, underwater/surface sink nodes, autonomous underwater vehicles (AUVs). In the proposed architecture, for the maximization of packet delivery ratio and the minimization of underwater sensor's energy consumption, a hybrid routing protocol is used. More specifically, cluster members use Tree based routing to transmit sensing data to clusterheads. AUVs on optimal trajectory movements collect the aggregated data from clusterhead and finally forward the data to the sink node. Also, in order to minimize the maximum travel distance of AUVs, an Integer Linear Programming based algorithm is employed. Performance analysis through simulations shows that the proposed architecture can achieve a higher data delivery ratio and lower energy consumption than existing routing schemes such as gradient based routing and geographical forwarding. Start after striking space key 2 times.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.5
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• pp.853-858
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• 2022

In this paper, we show a simultaneous transmission of underwater optical wireless power transfer and underwater optical wireless communication. A laser diode is used for electric-to-optic conversion at the transmitter and a solar cell is used for optic-to-electric conversion at the receiver. We optimized the transmitter and receiver for the best performance. The laser diode is a 100-mW laser diode and showed a conversion efficiency of 18.5%. The experimental results showed a 0.33-% DC-to-DC underwater power transfer efficiency at 5 m and a data rate of 100 kbps at 1 m.

• Explosives and Blasting
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• v.28 no.2
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• pp.119-132
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• 2010

There are many dispute with a construction due to such environment problem as vibration and noise. Generally, we have a standard for acceptance level in land. But we have not a sufficient standard for acceptance level or guide line in underwater sound. In other countries, a acceptance level or guide line in underwater sound has been suggested. Especially the management criterion of underwater noise for fish has bee suggested using the measurement data (peak pressure, rms, energy and SEL) by a hydrophone. In Korea, there is no management criterion of underwater noise for fish. This study suggested the management criteria of underwater noise for fish based on the measured data by a hydrophone.