• The Microorganisms and Industry
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• v.15 no.1
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• pp.10-15
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• 1989

자연수계 생태계는 해양, 하천, 호수, 지하수 등과 같이 그 특성에 따라 많은 종류로 구분할 수 있는데, 그중에서 하구는 물리, 화학적 성질은 물론 미생물을 포함한 많은 생물이 끊임없이 변천(transition)하는 생태계의 하나의 꼽을 수 있다. 환경의 변화는 수온, 염분, pH, Eh, 투명도, 부유물질 등의 변화를 포함하는데, 하구 감조수역에서 가장 심한 변화를 일으키는 것은 일반적으로 영양염류의 양과 종류, 수온, 염분 등이다(Morita et al., 1973: Rublee et al., 1984). 그러므로 본 연구에서는 1985년 7월부터 1986년 12월까지 낙동강에 위치한 3개 정점에서 물리, 화학적 환경, 영양염류, BOD, 세균 및 heterotrophic activity의 28개 변수의 변화를 살펴보았다. 이렇게 측정된 결과를 중회귀 및 요인 분석으로 생태계에서 세균의 분포와 활성에 미치는 영향을 분석하고자 한다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.846-855
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• 2021

Eco-friendly and renewable energy sources are actively being researched in recent times, and of shore wind power generation requires advanced design technologies in terms of increasing the capacities of wind turbines and enlarging wind turbine installation vessels (WTIVs). The WTIV ensures that the hull is situated at a height that is not affected by waves. The most important part of the WTIV is the leg structure, which must respond dynamically according to the wave, current, and wind loads. In particular, the wave load is composed of irregular waves, and it is important to know the exact dynamic response. The dynamic response analysis uses a single degree of freedom (SDOF) method, which is a simplified approach, but it is limited owing to the consideration of random waves. Therefore, in industrial practice, the time-domain analysis of random waves is based on the multi degree of freedom (MDOF) method. Although the MDOF method provides high-precision results, its data convergence is sensitive and difficult to apply owing to design complexity. Therefore, a dynamic amplification factor (DAF) estimation formula is developed in this study to express the dynamic response characteristics of random waves through time-domain analysis based on different variables. It is confirmed that the calculation time can be shortened and accuracy enhanced compared to existing MDOF methods. The developed formula will be used in the initial design of WTIVs and similar structures.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.992-1001
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• 2023

OWEC (Overtopping Wave Energy Converter) is a wave power generation system using the wave overtopping. The performance and safety of the OWEC are affected by wave characteristics, such as wave height, period. To mitigate this issue, optimal OWEC designs based on wave characteristics must be investigated. In this study, the environmental conditions along the Ulleungdo coast were used. The hydraulic efficiency of the OWEC was calculated using SPH (Smoothed Particle Hydrodynamics) by comparing 4 models that changed the substructure. As a result, it was possible to change the substructure. Through design optimization, a new truss-type structure, which is a substructure capable of carrying the design load, was proposed. Through a case study using member diameter and thickness as design variables, structural safety was secured under allowable stress conditions. Considering wave load, the natural frequency of the proposed structure was compared with the wave period of the relevant sea area. Harmonic response analysis was performed using wave with a 1-year return period as the load. The proposed substructure had a reduced response magnitude at the same exciting force, and achieved weight reduction of more than 32%.

• Journal of the Korean Institute of Gas
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• v.27 no.1
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• pp.13-22
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• 2023

As an alternative to environmental pollution generated from fossil fuels currently in use, research is being actively conducted to use hydrogen that does not cause air pollution. As fire and explosion accidents caused by hydrogen leakage have occurred until recently, research on safety is needed to commercialize hydrogen on ships, which are special environments. In this study, a seasonal alternative scenario for each season and the worst scenario were assumed in the event of a leakage accident while a hydrogen fuel cell propulsion ship equipped with a hydrogen storage tank was navigating at JangSaengPo port in Ulsan. In order to consider environmental variables, the damage impact range was derived through ALOHA and probit analysis based on the annual average weather data for 2021 by the Korea Meteorological Administration and on geographic information data from the National Statistical Office. Radiation showed a wider damage range than that of Overpressure and Flame in both the alternative and worst-case scenarios, and as a result of probit analysis, a fatality rate of 99% was confirmed in all areas.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.523-532
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• 2006

It is thought that the suggestion of efficient and rational design guideline based on the behavior evaluation of bridge structure system the included cross beam is necessary for the construction efficiency of two-I girder steel bridges. Therefore, in this study, the effects of influence parameters are investigated by the behavior analyses of the bridges, in which the influence parameters are location, spacing and rigidity of the cross beam. For this study, the existed two-I girder steel bridges firstly were selected with the model of case study and the FE analyses for some case models were performed to estimate the action of the cross beam in the bridge. From the analyses, it was estimated that if it consider local stress and load distribution of a floor system, shell and solid elements are compatible to modeling of the cross beams. Also, the efficient design guideline for the cross beam of two-I girder steel bridge was suggested from parameter studies used location, spacing and rigidity of the cross beam.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.4
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• pp.403-409
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• 2013

Shear behavior of concrete beams reinforced with steel and/or FRP bar is studied through experimental tests. Experimental parameters includes the mechanical properties of reinforcements in shear and bending, and the ratio of shear reinforcement. The validity of the modified truss analogy, that has been widely accepted as a basis for the practical shear design of concrete beams, has been examined thoroughly by analyzing experimental results. The experimental results indicate that the modified truss analogy cannot be directly adopted to the shear problem of concrete beams reinforced with FRP bar.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.4
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• pp.347-351
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• 2008

In this paper, a new co-planar waveguide ultra-wideband aperture is designed as wireless application in ships. The designed antenna consists of a rectangular aperture on a determined ground plane and a mushroom shaped stub. The mushroom-shaped stub, which is simple, convenient to analyze and optimise, has less parameters. This antenna has compact aperture size $21.1{\times}8.1mm^2$, designed on FR-4 substrate with dielectric constant of 4.3, thickness of 1.5mm. CPW fed planar antenna has the advantages of wide-bandwidth, low-cost and easy interaction with the radio frequency front end circuitry.

• Journal of the Korean Society for Marine Environment & Energy
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• v.5 no.3
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• pp.35-44
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• 2002

In this paper, the analytic studies on the wave control performance of moored pontoon-type floating breakwater are presented. A two-dimensional eigenfunction expansion method is adopted to study the motion responses and the transmission coefficients of pontoon-type floating breakwater in beam waves. The stiffness coefficients of mooring line are idealized as linear elastic spring. Comparison of the analytical results with a numerical results (FEM) shows good agreement over a wide range of frequencies. The performance of mooed pontoon-type floating breakwater is tested with various design parameters such as sectional geometry, mooring line characteristics and wave frequencies. It is found that the properly designed floating breakwater can be an effective wave control structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.247-247
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• 2012

기존형광등보다 에너지소비가 적고, 수명이 길다는 장점을 가진 LED소자는 조명분야뿐만 아니라 선박 및 해양플랜트시장에까지 적용분야가 확대되고 있다. 그러나 LED소자의 수명연장 및 제품신뢰성을 위해서 방열에 관한 연구가 필수적이며 특히, 해양환경적용을 위해서는 내부식성을 요구하는 방열 재료개발에 대한 연구가 필요하다. 일반적으로 방열판소재로 사용되는 알루미늄의 경우 열전도도가 우수하며, 대기 중에서 쉽게 생기는 자연산화막보다 내부식특성을 향상시키기 위해 현재 국내 외의 표면처리 방법으로 전기화학적 방법을 이용한 Anodizing기술을 적용하고 있다. 하지만, Anodizing에 사용되는 질산과 황산액을 처리하는 과정에서 유독물질을 발생시킴으로 유해물질사용제한 등 국제적으로 환경규제가 강화되고 있어 Anodizing기술의 적용이 제한적인 단점이 있다. 본 연구에서는 친환경적 기술인 Plasma Immersion Ion Implantation (PIII)방식을 사용하여 알루미늄표면에 $Al_2O_3$을 형성하였다. 최적의 산화막증착 조건을 찾기 위해 Gas Flow양, Pulse Voltage, 공정온도, 시간 등을 변수로 실험을 진행하였다. SIMS (Secondary ion mass spectroscopy)를 통해 $Al_2O_3$ 박막두께 및 Oxygen의 정량분석을 하였으며, Anodizing처리된 알루미늄시편과 열전도특성과 내부식특성을 비교하기 위해 각각 Hot Disk 열전도율측정기와 Salt water tester chamber를 사용하였다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.3
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• pp.198-204
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• 2014

Ships sailing the seas encounter air resistance. The air resistance depends on the shape of the above-water hull, the ship speed, the wind speed and wind direction. The experimental or statistical methods which are used to predict the air resistance are one of the essential procedures of the calculation of the towing force of the disabled ships. This paper shows simplified air resistance prediction method using the variables of the projected area of the above-water hull, the speed of the ship, the wind speed and its direction. These methods have been applied to the existing computer program which had been set up to predict the towing force of the disabled ships.