• The KSFM Journal of Fluid Machinery
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• v.14 no.5
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• pp.48-54
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• 2011

Structural modifications of a ship may cause a fatal accident such as sinking and wrecking of ship. Especially, barge ship can be easily reconstructed to load more bulk cargo. In this study, for a real accident case, change of mooring force due to structural modification was analyzed to evaluate accident risk. A two dimensional dynamic model for the barge ship was constructed to compute mooring forces with related to floating motion. The equation of motion was established in Matlab code and buoyancy was calculated by using direct integration of submerged volume. The results showed that wind force, current force, and mooring force after rebuilding was approximately 4.3 kN, 14 kN, 1,561 kN respectively. The maximum force of mooring force according to the length of mooring cable were 1,614 kN at 30 m of mooring cable. Thus, an arbitrary modification of ship lead instability and unreliable result so that illegal rebuilding of ship should be avoided.

• Journal of Power System Engineering
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• v.12 no.6
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• pp.18-23
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• 2008

This paper describes development of real-time condition monitoring system to observe state of a container crane in a port. To analyze the state of a crane, the strength and the direction of wind are measured with sensors along with the load resulted a crane at the moment. The measured signals are processed by especially developed conditioning board and converted into digital data. Measured data are analyzed to define the state of the crane at an indicator. For transmission of these data to the indicator, we implemented wireless sensor network based on IEEE 802.15.4 MAC(Media Access Control) protocol and Bluetooth network protocol. To extend the networking distance between the indicator and sensor nodes, the shortest path routing algorithm was applied for WSN(Wireless Sensor Network) networks. The indicator sends the state information of the crane to monitoring server through IEEE 802.11 b wireless LAN(Local Area Network). Monitoring server decides whether alarm should be issued or not. The performance of developed WSN and Bluetooth network were evaluated and analyzed in terms of communication delay and throughput.

• Journal of the Korean housing association
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• v.24 no.1
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• pp.51-59
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• 2013

This study aims to improve the thermal comfort level of detached housing area by reducing the impact of thermal environment. The study focused on reducing surface temperature that is generated in buildings and adjacent spaces as a result of sensible heat load and presented a proposal on implementing planting method considering its outdoor condition and structure and composed materials. To perform the study, we utilized 3D-CAD to examine the outdoor condition and structure and composed materials that impact on surface temperature and conducted space design after reflecting climatic elements in simulations. The result is as follows. In reviewing temperature distribution of Heat Island Potential (HIP) of buildings and adjacent spaces, in case where green coverage ratio is increased, there was a $6^{\circ}C$ temperature difference and in regard to changes in the thermal environment in detached housing area, in case where rooftop planting, surface improvement, planting, and overall green coverage ratio is increased, there was a $10^{\circ}C$ temperature difference. In addition, there was difference in temperature in detached housing area following the changes in wind.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1304-1310
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• 2015

In remote islands, due to expense of existing generation systems, installation of photovoltaic cells (PVs) and wind turbines has a chance of reducing generation costs. However, in island power systems, even short-term power fluctuations change the frequency of grids because of their small inertia constant. In order to compensate power fluctuations, the authors proposed the power consumption control of pumps which send water to tanks. The power control doesn’t affect water users’ convenience as long as tanks hold water. Based on experimental characteristics of a pump system, this paper shows methods to determine reference power consumption of the system with compensation for short-term PV fluctuations while satisfying water demand. One method uses a PI controller and the other method calculates reference power consumption from water flow reference. Simulations with a PV and a pump system are carried out to find optimum parameters and to compare the methods. Results show that both PI control method and water flow calculation method are useful for satisfying the water demand constraint. The water demand constraint has a little impact to suppression of the short-term power fluctuation in this condition.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.452-453
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• 2008

본 논문에서는 송전철탑에 작용하는 설계하중으로서 [송전철탑 설계풍속에 관한 연구]에 근거하여 1987년 6월 제정된 지역별설계 풍하중기준의 개정을 위한 연구결과를 수록하였다. 당시 제정된 송전설계기준은 이전에 전국적으로 통일시켜 적용되던 풍속압($76kg/m^2$)을 지역별 풍속을 구분하여 그 차이에 따라 I, II, III, 지역 및 울릉도로 구분하여 차등 적용하였으며, 본 연구에서는 국내 기상청이 생긴 이래 2005년까지 누적된 기상 DB의 분석을 통하여 최근의 기상 현상을 반영한 보다 현실적인 설계기준 개정과정을 수록하였다. 본 논문에서는 1980년대 후반부터 약 20년간의 기상청의 풍향, 풍속자료를 추가로 확보하여 이를 분석하고 재현기간을 반영한 지역별 설계하중을 재산정하여 최근의 기상자료를 포함하여 보다 정확한 분석을 도모하고, 사회 환경의 급변함에 따라 우려되는 기상이변 등을 고려한 안전성과 경제성이 향상된 설계기준의 산정과정을 고찰하고자 한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.5
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• pp.42-49
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• 2009

The effects of various forces acting on concrete pole are analyzed using finite element method how the forces affect on ground displacement. The soil types, wind load location of anchor block embedded depth of pole, and distance between poles are varied to find out effects on lateral displacement. Anchor block is effective when it is located at 1/4 of embedded depth The displacement is decreases as elastic modulus increases. Concrete reinforcement for loosened ground is necessary for double poles because double poles cause large excavation. When embedded depth ratio decrease, lateral displacement increase as closer to ground surface. Large embedded depth is effective to reduce lateral displacement, and the distance between poles is not much large factor.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.12
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• pp.1111-1120
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• 2010

A variety of materials may be used for soundproof panels. The major advantage of transparent material over traditional materials in noise barriers is aesthetics. The transparent panel materials such as clear plastic or glass are an ideal way of reducing or virtually eliminating the visual impact of a noise barrier. With the use of transparent materials, the drivers' view of the roadside and the sunlight penetration to the highway would not be blocked. Korean Industrial Standards for soundproof panels have been established. But, transparent soundproof panels are not included in this standards. And, some specifications provide only a few basic characteristics for transparent soundproof panels. To develop guidelines on quality criteria for transparent soundproof panel, their mechanical properties such as wind load resistance, safety under impact, and abrasion resistance were experimentally investigated.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.423-426
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• 2009

POSTECH Graduate School of Wind Energy is trying to upgrade the PMSG used for Unison U50 to 900 kW class. Intensive optimization efforts are carried out the reduce the axial size and total weight of the generator while increasing the rated output to 900 kW. The generator features 3.32m stator inner radius, 671mm stator length, 84 pole, 25 rated rpm and 31.6kN/$m^2$ shear force density. To reduce the gross weight, the stronger magnetic material is applied with optimal magnet size resulting lowest cogging torque. Also, instead of stator skewing the stator, the magnet position along the circumference is optimized to further reduce the cogging torque. This scheme eliminates the stator skewing procedure and may enhance the productivity. This method also reduces the total harmonic distortion. In this report, upgrade method, no-load line to line voltage and phase voltage, cogging torque, loss calculations and thermal analysis are presented.

• New & Renewable Energy
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• v.10 no.2
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• pp.5-11
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• 2014

Squirrel cage induction motor is the main driving system of industrial field and familiar with its use in a large variety of applications. The structure and operating characteristics of induction generator is almost identical to induction motor, but the induction generator part is used restrictively from hydropower power and wind power development etc. Recently induction generator is commonly used for micro & small hydro power applications due to its simplicity, reliability, low cost and robustness. Input and output of induction motor has turned against at the induction generator operation. Rotation speed of induction generator is small faster than synchronous speed of induction motor. As output of induction machines increases with the increasement of speed, so loss is same. Actually, generator efficiency is lower than motor at this condition. If induction generator is connected with mechanical load such as increaser, total efficiency is decreased. Consequently the quality in compliance with an induction motor parameter applying like that in the generator is a possibility of having the error of some. In this paper, we analyzed that input, output, torque and efficiency of induction machine is different from each other above and below synchronous speed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.495-496
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• 2014

The suction method is the substructure installation using the water pressure difference generated by discharging water inside the pile by the pumping operation, after the intrusion by the self-weights of a large hollow steel pipe or a concrete structure. It is known as the low-noise and low-vibration method against the general pile driven method and eco-friendly, also. Most current design and safety assessment of the support structure and considering only the static load, however, the importance of dynamic behavior becomes magnified as the size of wind power generator increases. This study measures the natural frequency of the suction pile prototype about the penetration depth as a part of basic research and analyzed the interaction between the soil and the structure.