• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.523-526
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• 2013

In order to purify the waste water containing natural fatty oil, hydroxy radical and/or ozone are used to remove the fatty oil dispersed in the waste water. The fatty oil is decomposed by oxidation reaction through hydroxy radical and ozone, and eliminated as a function of first order reaction. It is clearly confirmed that the fatty oil in waste water can be effectively removed much more in the use of both hydroxy radical and ozone than only hydroxy radical as an oxydant. In addition, the decomposition chemical reaction mechanism of the fatty oil by hydroxy radical and ozone is proposed.

• Proceedings of the Korea Contents Association Conference
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• 2008.05a
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• pp.33-37
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• 2008

The interaction between artificial fish and aquatic surroundings and the fish's realistic locomotion are very important elements to construct virtual aquariums. In general, the artificial fish in virtual aquariums used to be created by 3D modeling tools, and was repeatedly showing the simple and constant form of swimming. This paper will analyze the sorts of biological forms of fish-swimming and the propelling and turning characteristics. Then, we propose a method of the basic swimming and turning of artificial fish to generate various and natural-looking locomotion. It is possible to make a explorable virtual aquarium more immersive by using interactive interfaces together.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.33-39
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• 2017

A top priority in the design of underwater vehicle is to guarantee the dependability of the electric system because failure of the electrical power supply system is directly related to the life of the passengers. In this paper, we present four kinds of alternative designs to improve reliability of electrical system in underwater vehicle. To reduce the risk and to increase availability of the electrical system, we use the redundancy of the grid structure and power converter. For all design alternatives, we carry out Fault Tree Analysis. Based on the FTA result, we implement RAM simulation to compare the risk and availability for the proposed design alternatives.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.3
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• pp.41-50
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• 1993

This paper compares various potential based panel methods for the analysis of two-dimensional hydrofoil. The strength of singularity on each panel is assumed to be constant or linear. Robin boundary condition as well as Neumann and Dirichlet boundary conditions are applied to various formulations to evaluate the accuracies of the methods. Pressures and lifts are computed for various two-dimensional hydrofoil geometries and are compared with the analytic solutions. Extensive studies are performed on the local errors near the trailing edge, known to be sensitive to the foil geometry with sharp trailing edge and high camber. Robin boundary condition with the perturbation velocity potential formulation shows the best accuracy and convergence rate.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.2
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• pp.129-135
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• 1999

The telemetry system for the current speed and direction, the underwater ambient noise and the distribution ecology of fishes was constructed by the author and his collaborator in order to product and manage effectively in shallow sea culture and setnets fisheries, and then the experiments for the telemetry system carried out at set net fishing ground located Nungpobay in Kojedo from October 1996 to June 1997. As this results, the techniques suggested in the telemetry system gave full display its function even though far away 1.5 km from transmitting part, but with the suggested telemetry system could not be ascertained relationship between physical environment and distribution ecology of fishes.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.21 no.2
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• pp.233-249
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• 1976

This experiment was conducted in an attempt to find the variation of growth, yield components and .yield in accordance with different seeding rate and fertilizer level. The degree of yield increase by increased fertilizer level was higher in heavy spike type .than in high tiller type. but that by increased seeding rate was the reverse in barley and wheat. 1, 000 .grains weight and maturity was increased by increased fertilizer level in heavy spike type (Haganemugi and Young Kwang) but decreased in high tiller type (Suweon ＃165 and Yuk Seung＃3).

• Strategy21
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• s.41
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• pp.333-370
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• 2017

북한의 SLBM 위협이 대한민국 안보에 미치는 영향에 대해 그동안 많은 논의가 있어 왔지만, 북의 잠수함에서 발사하는 탄도미사일이 보유한 진정한 위협에 대한 인식은 아직도 부족한 듯하다. 그 이유는 대부분의 논의가 북 SLBM 기술의 성숙도와 완성시기 등 기술적 수준에 관심이 치우쳐져 있기 때문이다. 핵전략과 억제전략의 관점에서 본다면 북한의 SLBM 개발은 한미동맹의 제1격에 대한 완벽한 제2격 능력 보유에 그 핵심이 있다. 즉 향후 개발될 북한의 SLBM은 평양 김정은 정권의 생존을 보장할 직접적이고 핵심적인 전력이 될 것이다. 이는 궁극적으로 한미 군사동맹과 북한의 현 군사력 균형을 깨뜨리고 앞으로 북의 군사도발 가능성을 더욱 높이는 결과를 가지고 올 것이다. 북의 핵전략은 현재 확증보복(assured retaliation) 단계로 발전하고 있으며, 결국에는 전쟁에 사용될 전술적 핵무기 능력(war-fighting capability)을 갖게 될 것이다. 이에 대한민국 해군은 우리의 강점을 활용하여 적의 약점을 공략할 수 있는 상쇄전략(offset strategy)을 개발하여야 한다. 북한의 현 제한된 잠수함 기술력과 대잠작전 능력을 고려할 때 한국해군은 수중영역에서의 공세적 대잠전(offensive ASW) 개념을 보다 발전시켜야만 할 것이다. 이는 미 해군이 냉전기간 중 소련해군 핵추진전략잠수함(SSBN) 대응을 위해 발전시킨 전략대잠전(strategic ASW) 개념에서 교훈을 얻을 수 있다. 미 해군은 소련 해군의 SSBN 을 억제하기 위해 공세적인 전략대잠전을 수행했고 그 결과 소련해군은 자국의 연안에서 벗어나지 못하는 요새전략(bastion strategy)를 추구할 수밖에 없었다. 당시 미 해군의 전략대잠전은 공격잠수함(SSN), 대잠초계기, 수중 탐지체계(SOSUS), 공격기뢰 등의 전력으로 구성되었다. 따라서 북한 SLBM 에 대한 한국해군의 전략개념은 북의 핵전략(제 2 격능력)을 억제하는 방향으로 정립되어야 하며, 이를 위한 해군력 건설은 대잠전 능력 강화에 초점을 맞추어야 한다. 우리 해군은 장기적으로 핵추진잠수함을 비롯하여 성능이 향상된 대잠초계기, 한반도 해역을 중심으로 한 미 해군의 SOSUS 와 유사한 수중탐지장비 그리고 장시간 수중작전이 가능한 무인잠수정(UUV)을 도입해야만 한다. 단기적으로는 현재 추진되고 있는KAMD 체계에 SM-3 를 보유한 이지스함을 포함시켜, 북 SLBM 에 대한 요격능력을 강화해야 할 것이다. 한미동맹은 북 핵전략의 핵심전력인 SLBM 개발에 대한 위협인식을 공유해야만 하다. 작전적 수준에서는 양국 해군 간 대잠전 및 대유도탄전 작전운용성 증대에 우선순위를 두고, 기존의 한미 간 연합작전능력 강화뿐 아니라 위기시를 대비하여 미일 간 구축되어 있는 대잠전 및 대유도탄전 능력도 활용할 필요가 있을 것이다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.336-339
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• 2011

In the RTLS(Real Time Location Based System), in case of existing a number of moving target, extremely complecated data flow is can be occurred. In the network where single gateway exists, various data which was collected from sensor node is transmitted along the simple route as time goes by. In case of multi-gateway configuration, the collected data is transmitted through diverse routes rather than simple route. This kind of data causes jams on nodes and this brings down the performance of the network. Different from existing studies, in this thesis, MAC (Media Access Control) protocol which minimizes data collision between nodes and guarantees QoS(Quality of Service) is suggested, in order to communicate efficiently in multi-gateway underwater sensor network environment. In the suggested protocol, source node which wants to transmit data makes a channel reservation to a number of destination node using a RTS packet. Source node reserves a channel without collision, by scheduling CTS response time using expected delay information from neighbor nodes. Once the reservation is made, source node transmit data packet without collision. This protocol analyzes/estimates the performance compared to a method provided from existing studies via simulation. As a results of the analysis, it was comfirmed that the suggested method has better performance, such as efficiency and delay.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.4
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• pp.228-233
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• 2022

This study is an experimental study on how to use phase change materials(PCM) to generate electrical energy for long-term operation of underwater unmanned vehicles. The electrical energy generation method is a volume change and a pressure change that occur as a phase change material changes to a solid or liquid state according to temperature, and the change in pressure creates a flow of fluid to create electrical energy. Polyethylene glycol was used as a phase change material considering the temperature of the ocean. In addition, an electrical energy generating device that converts volume change into pressure at low temperature (1℃~2℃) in solid state and high temperature (21℃~25℃) in liquid state was fabricated. As a result of the experiment, the pressure change according to the phase change rapidly changed between 1 hour and 2 hours, and maintained a pressure of about 24MPa after 4 hours. Through this, it was confirmed that it can be used as a power source for underwater unmanned vehicles using phase change materials and temperature differences. In addition, it was found that a more improved design should be made in order to apply the phase change material to an underwater unmanned vehicle.

• The Journal of the Acoustical Society of Korea
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• v.41 no.6
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• pp.610-620
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• 2022

An acoustic vector sensor can simultaneously receive vector quantities, such as particle velocity and acceleration, as well as acoustic pressure at one location, and thus it can be used as a single input multiple output receiver in underwater acoustic communication systems. On the other hand, vector signals received by a single vector sensor have different channel characteristics due to the azimuth angle between the source and receiver and the difference in propagation angle of multipath in each component, producing different communication performances. In this paper, we propose a channel parameter-based weighting method to improve the performance of an acoustic communication system using a single vector sensor. To verify the proposed method, we used communication data collected from the experiment conducted during the KOREX-17 (Korea Reverberation Experiment). For communication demodulation, block-based time reversal technique which is robust against time-varying channels were utilized. Finally, the communication results showed that the effectiveness of the channel parameter-based weighting method for the underwater communication system using a single vector sensor was verified.