• Water for future
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• v.20 no.4
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• pp.249-256
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• 1987

Wave forces on fixed two-dimensional objects submerged in water of finite depth were analysed by Boundary Element Method using linear elements.It is assumed that the wave forces may be described by linear theory and that incident wave direction is normal to the objects of infinite length. In this paper, wave forces on a bottom-seated half cross section pipeline, a circular pipeline, a submerged pipeline and submerged breakwater of arbitrary shape were studied. The accuracy of the computational scheme is investigated by comparing the numerical results with the existing laboratory results and analytical solutions of other researchers.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.4
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• pp.231-237
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• 1999

A geometric non-linear finite element formulation of spatial ocean cable under currents is presented using multiple noded curved cable elements. Tangent stiffness and mass matrices for the isoparametric cable ele¬ment are derived and the initial equilibrium state of ocean cable subjected to self-weights, buoyancy, and current as well as support motions is determined using the load incremental method. Free vibration analysis of ocean cables is performed based on the initial equilibrium configuration. Numerical examples are presented and discussed in order to demonstrate the feasibility of the present finite element method and investigate dynamic characteristics of ocean cables.

• 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).

• Explosives and Blasting
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• v.37 no.3
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• pp.13-24
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• 2019

This paper was prepared to investigate the behavior of fragments in underwater torpedo explosion beneath a frigate or surface ship by using an explicit finite element analysis. In this study, a fluid-structure interaction (FSI) methodology, called the multi-material arbitrary Lagrangian-Eulerian (MM-ALE) approach in LS-DYNA, was employed to obtain the responses of the torpedo fragments and frigate hull to the explosion. The Euler models for the analysis were comprised of air, water, and explosive, while the Lagrange models consisted of the fragment and the hull. The focus of this modeling was to examine whether a worst-case fragment could penetrate the frigate hull located close (4.5 m) to the exploding torpedo. The simulation was performed in two separate steps. At first, with the assumption that the expanding skin of the torpedo had been torn apart by consuming 30% of the explosive energy, the initial velocity of the worst-case fragment was sought based on a well-known experimental result concerning the fragment velocity in underwater bomb explosion. Then, the terminal velocity of the worst-case fragment that is expected to occur before the fragment hit the frigate hull was sought in the second step. Under the given conditions, the possible initial velocities of the worst-case fragment were found to be very fast (400 and 1000 m/s). But, the velocity difference between the fragment and the hull was merely 4 m/s at the instant of collision. This result was likely to be due to both the tremendous drag force exerted by the water and the non-failure condition given to the frigate hull. Anyway, at least under the given conditions, it is thought that the worst-case fragment seldom penetrate the frigate hull because there is no significant velocity difference between them.

• 재활복지
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• v.20 no.4
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• pp.177-201
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• 2016

The purpose of this study is to develop systematical components and implementation of rehabilitation physical activity by analyzing the relative importance among each factor. To achieve the purpose of this study, 20 participants were selected, and they consisted of instructors and adapted physical activity teachers and professional who have experiences in institutes and hospital where have operate program related to rehabilitation physical activity and adapted physical activity program. Delphi technique was conducted for three times by the participants. For the decision of priorities about improvement factors, AHP was performed. The results were as follows. As the result of this study, the factors of the rehabilitation physical activity consisted of six type of exercise; fitness, psychological exercise, aquatic exercise, sense & perception exercise, ambulatory exercise, and motor skills. Also, 21 sub-factors were also extracted. The result from analyzing the priorities of factors was fitness 33.2%, aquatic exercise 20.6%, psychological exercise 16.3%, sense & perception exercise 11.7%, ambulatory exercise 10.8% and motor skills 8.6%. Also, among results from the weighted state of priority factors, muscular strength and endurance were the most importance factor which had 23.4% weighting, and meditation was the least importance factor which had 0.5% weighting.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.3
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• pp.164-173
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• 2014

In underwater robotics, vision would be a key element for recognition in underwater environments. However, due to turbidity an underwater optical camera is rarely available. An underwater imaging sonar, as an alternative, delivers low quality sonar images which are not stable and accurate enough to find out natural objects by image processing. For this, artificial landmarks based on the characteristics of ultrasonic waves and their recognition method by a shape matrix transformation were proposed and were proven in Part 1. But, this is not working properly in undulating and dynamically noisy sea-bottom. To solve this, we propose a framework providing a selection phase of likelihood candidates, a selection phase for final candidates, recognition phase and tracking phase in sequence images, where a particle filter based selection mechanism to eliminate fake candidates and a mean shift based tracking algorithm are also proposed. All 4 steps are running in parallel and real-time processing. The proposed framework is flexible to add and to modify internal algorithms. A pool test and sea trial are carried out to prove the performance, and detail analysis of experimental results are done. Information is obtained from tracking phase such as relative distance, bearing will be expected to be used for control and navigation of underwater robots.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.6
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• pp.521-527
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• 2016

This paper is concerned with the numerical analysis of dynamic response of floating offshore wind turbine subject to underwater explosion using an effective non-reflecting technique. An infinite sea water domain was truncated into a finite domain, and the non-reflecting technique called the perfectly matched layer(PML) was applied to the boundary of truncated finite domain to absorb the inherent reflection of out-going impact wave at the boundary. The generalized transport equations that govern the inviscid compressible water flow was split into three PML equations by introducing the direction-wise absorption coefficients and state variables. The fluid-structure interaction problem that is composed of the wind turbine and the sea water flow was solved by the iterative coupled Eulerian FVM and Largangian FEM. And, the explosion-induced hydrodynamic pressure was calculated by JWL(Jones-Wilkins-Lee) equation of state. Through the numerical experiment, the hydrodynamic pressure and the structural dynamic response were investigated. It has been confirmed that the case using PML technique provides more reliable numerical results than the case without using PML technique.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.863-874
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• 2015

The use of pile reinforcement is considered as one of the most promising techniques for improving load carrying capacity of piles in offshore area. In this study, to consider the horizontal and uplift bearing capacity of submerged breakwater bearing pile, exclusive analysis on load-transfer behaviour of pile was conducted. First of all, check the reinforcing effect from the three-dimensional finite element method, and estimate load transfer curve (ground reaction force). Based on these results, the reinforcing effect was quantified by estimating the coefficients of horizontal and uplift reinforcement of reinforced piles. Load transfer function with consideration of the reinforcing effect was proposed from estimated coefficients. A comparison of the analysis using the proposed load transfer function with three-dimensional finite element analysis has resulted that the proposed load transfer function is displaying good accuracy of predicting behavior of the load transfer between the pile and soil reinforcement. Interpretation of the submerged structure by applying a load transfer function considering the reinforcing effect, has shown that the reinforced pile's shear, bending moment and displacement are less than that of non-reinforced piles, while the subgrade reaction modulus arises greater. Thus, it is expected to be relatively cost effective in terms of design.

• Journal of KSNVE
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• v.12 no.6
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• pp.429-436
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• 2002

함정에 있어서 수중 표적의 탐지나 식별, 피탐 위험으로부터 회피 등은 함정의 생존성과 직결되는 사항으로 방사소음을 최소화하는 함정 음향 스텔스가 중요한 요소이다. 함정의 음향분야 시험평가 결과는 신조함정의 기준 만족도 평가뿐만 아니라 음향식별 정보추출/DB구축, 소음통제 방안설정 및 피탐지 위험성 평가 등 전반적인 음향작전 능력 향상에 활용되고 있다.(중략)

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.357-358
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• 2001

산소는 모든 육상 동식물뿐만 아니라 수중 동식물의 생명 유지에 가장 필수적인 요소이다. 양식에 있어 산소는 고밀도 사육시 환경 수용력을 조절하는 요인으로 그 중요성은 생물학적 그리고 경제적인 면에서도 강조되고 있다. 산소 소비량에 대한 연구는 담수어류를 대상으로 꾸준히 진행되어 오고 있으나, 해산어류의 경우 산소 소비량과 관련한 연구는 미흡한 실정이다(Honda 1988; Kikuch et al., 1990; Lemarie et al., 1988). 해산어류를 대상으로 한 산소소비량의 연구는 주로 채수를 통하여 측정하였기 때문에 단위 시간당 측정할 수 있는 횟수는 한정되어 있어 정확한 산소 소비량을 산출하기 어렵다. (중략)