• Smart Structures and Systems
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• v.15 no.2
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• pp.283-297
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• 2015

Jacket-type offshore structures are always exposed to severe environmental conditions such as salt, high speed of current, wave, and wind compared with other onshore structures. In spite of the importance of maintaining the structural integrity for an offshore structure, there are few cases to apply a structural health monitoring (SHM) system in practice. The impedance-based SHM is a kind of local SHM techniques and to date, numerous techniques and algorithms have been proposed for local SHM of real-scale structures. However, it still requires a significant challenge for practical applications to compensate unknown environmental effects and to extract only damage features from impedance signals. In this study, the impedance-based SHM was carried out on a 1/20-scaled model of an Uldolmok current power plant structure in Korea under changes in temperature and transverse loadings. Principal component analysis (PCA)-based approach was applied with a conventional damage index to eliminate environmental changes by removing principal components sensitive to them. Experimental results showed that the proposed approach is an effective tool for long-term SHM under significant environmental changes.

• Journal of Ocean Engineering and Technology
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• v.31 no.6
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• pp.379-387
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• 2017

In this study, a pile-guide mooring system (PGMS) was designed for an offshore liquefied natural gas bunkering terminal (LNG-BT), which is an essential infrastructure for large LNG-fuelled ships. The PGMS consisted of guide piles to restrict five motions of the floater, except for heave, as well as a seabed truss structure to support the guide piles and foundation piles to fix the system to the seabed. Singapore port was considered for a case study because it is a highly probable ports for LNG bunkering projects. The wave height, current speed, and wind speed in Singapore port were investigated to calculate the environmental loads acting on the hull and PGMS. A load and resistance factor approach was used for the structural design, and a finite element analysis was performed for design verification. The steel usage of the PGMS was analyzed and compared with the material usage of a gravity-based structure under similar LNG capacity and water depth criteria. This paper also describes the water depth limit and wave conditions of the PGMS based on estimation of the initial investment and the present value profit difference. It suggests a suitable LNG-BT support system for various design conditions.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.608-612
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• 2012

To reduce these costs and time by finite element analysis program has been much research (3~4). At virtual CAE program as like Abaques, Ansys, Ls-dyna and Nastran, the input data of material is got bellow coupon test. In case of carbon composite, it is also put in lamina/laminate properties. There have big problem. If you want to simulate FW(filament winding or wind blade) how do you input material data. Each area of FW is different stacking conditions. It's too hard that each area is tested for inputting lamina or laminate properties. The composite structure increasing load is applied occurred as the matrix dependence of the crack-induced nonlinearity and nonlinear mobility appears since the initial damage. And uni-direction for this research applies the theory to have been confined to. On this study, we are going to get basically fiber properties and matrix than carbon composite properties for simulating according stacking method by GENOA-MCQ. It is help to simulate easily composite material. Also Calculate the matrix nonlinear for simulating non-linear.

• Journal of Biosystems Engineering
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• v.40 no.4
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• pp.305-313
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• 2015

Purpose: This study was performed to predict the fatigue life of a crank-type rotavator operated in domestic soil conditions using Recurdyn$^{(R)}$, a dynamic analysis program. Methods: Torque on the PTO shaft was measured using experiments conducted on the uplands and paddy fields in Korea. On the basis of the experimental and analytical results, the fatigue life of the crank-type rotavator was predicted by constructing an S-N curve according to the GL (Germanischer Lloyd Wind Energie GmbH) guideline. Results: The torques experienced by the PTO shaft in the paddy soil and the uplands were in the range of 472~797 N m and 313~430 N m, respectively, for every condition. In case of load condition, the peak torques (846 N m, 770 N m) were applied for severe conditions, resulting in a maximum (von Mises) stress of 75 MPa at the crank arm. The fatigue life of the crank-type rotavator was predicted to be 1,167 h that satisfies the target value of 1,110 h, by substituting the analysis results into an S-N curve of crank arm. Conclusions: The fatigue life of the crank-type rotavator was within the target life for the studied soil conditions; however, further field experiments for various soil conditions would be required to verify the prediction results.

• Membrane Journal
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• v.21 no.2
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• pp.107-117
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• 2011

The all vanadium redox-flow battery (V-RFB) is investigating as one of large-scale power storage systems. Particularly, V-RFB is being investigated as one of the power storage systems for the load leveling and output power equalization of the power systems using renewable energy such as solar and wind. In this paper, it was explained for the principle and construction, recent research review, economy, element technology in V-RFB.

• Journal of Ocean Engineering and Technology
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• v.25 no.4
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• pp.1-6
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• 2011

The installation of a topside structure can be categorized into the following stages: start, pre-lifting, lifting, lifted, rotating, positioning, lowering, mating, and end of installation. The transfer of the module onto the floating spar hull occurs in the last three stages, from lowering to the end. The coupled multi-body motions are calculated in both calm water and in irregular waves with a significant wave height (1.52m). The effects of the hydrodynamic interactions between the heavy lifting vessel and the spar hull during the lowering and mating stages are considered. The internal forces caused by the load transfer and ballasting are derived for the mating phases. The results of the internal forces for the calm water condition are compared with those in the irregular sea condition. Although the effect of the pitch motion on the relative vertical motion between the deck of the floating structure and the topside module is significant in the mating phases, the internal force induced pitch motion is too small to have this influence. However, the effect of the internal force on the wave-induced heave responses in the mating phases is noticeable in the irregular sea condition because transfer mass-induced draught changes for the floating structure are observed to have higher amplitudes than the external force induced responses. The impacts of the module on the spar hull in the mating phase are investigated.

• Journal of Ocean Engineering and Technology
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• v.25 no.4
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• pp.7-11
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• 2011

The installation phase for a topside module suggested can be divided into 9 stages, which include start, pre-lifting, lifting, lifted, rotating, positioning, lowering, mating, and end of installation. The transfer of the topside module from a transport barge to a crane vessel takes place in the first three stages, from start to lifting, while the transfer of the module onto a floating spar hull occurs in the last three stages, from lowering to the end. The coupled multi-body motions are calculated in both calm water and in irregular waves with significant wave height (1.52m), with suggested force equilibrium diagrams. The effects of the hydrodynamic interactions between the crane vessel and barge during the lifting stage have been considered. The internal forces caused by the load transfer and ballasting are derived for the lifting phases. The results of these internal forces for the calm water condition are compared with those in the irregular sea condition. Although the effect of pitch motion on the relative vertical motion between the deck of the floating structure and the topside module is significant in the lifting phases, the internal force induced pitch motion is too small to show its influence. However, the effect of the internal force on the wave-induced heave responses in the lifting phases is noticeable in the irregular sea condition because the transfer mass-induced draught changes in the floating structure are observed to have higher amplitudes than the external force induced responses.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.5
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• pp.498-509
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• 2015

The existing mobile antenna networks in the military use have been operated by the manual pointing between two antennas. The work presented here describes the study of ATPC(Automatic Tracking and Pointing Control) system between facing antennas and the related tracking and pointing performances. This system is able to automatically track the maximum RSSI(Received Signal Strength Indication) value from the source's RF(Radio Frequency) signal and then control for maintaining the LOS(Line of Sight) between two antennas. The system has three major units; the driving unit consisting of motors, harmonic drives and encoders, the sensor unit with a GPS(Global Positioning System) and AHRS(Attitude and Heading Reference System) and the control unit regulating all the tracking and pointing events. By using PI(Proportional and Integral) controller, this system is able to properly track and point the other antenna under the external disturbance like the wind load. Both the simulation and the experimental works have been successively carried out to prove the performances of the system.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.409_411
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• 2009

국내의 송전선 지지물 설계는 전기설비기술기준과 한국전력공사 송전설계기준에 근거하여 적용되며, 철탑하중에 큰 비중을 갖는 풍하중기준은 1985년 기상청의 풍속 데이터를 반영하여 1987년경에 제정된 지침을 지금까지 적용하고 있다. 당시 제정된 설계기준에서는 지역별 풍속 차이에 따라 I, II, III, 지역 및 울릉도로 구분하여 차등 적용하는 설계개념으로 주변여건을 고려하지 않고 동일한 지역내에 위치하고 있는 송전지지물의 경우에는 동일한 풍하중을 적용하는 방식이다. 최근 해외 철탑설계기준과 국내 건축물 설계기준에서는 전산기술의 발달로 국부적인 지형영향을 고려하여 철탑별로 개별적인 풍하중을 산정하는 방식을 채택하고 있다. 본 논문에서는 상용 송전선로 설계가 진행되고 있는 군산-새만금 예정 경과지 가운데 지형조건을 고려한 풍속할증이 요구되는 개소에 대한 설계 풍하중 검토사례를 소개한다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.6
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• pp.1093-1099
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• 2009

Alternative energy sources such as renewable energy like solar power systems, wind power systems, or fuel cell power systems has been the rising issue in the electrical power system. This paper discusses an economic study analysis of fuel cells in the korean electricity market. It includes the basic concept of a fuel cell and the korean electricity market. It also describes the need of renewable energy and how the fuel cell is connected with the local grid. This paper shows the impact of production and recovering thermal energy of a grid-connected fuel cell power system. The profit maximization approach has been structured including electrical power trade with the local grid and heat trade within the micro-grid. The strategies are evaluated using a local load that uses electric and thermal power which has different patterns between summer and winter periods. The solution algorithm is not newly developed one, but is solved by an application called GAMS. Results indicate the need and usefulness of a fuel cell power system.