• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.85-91
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• 2015

We investigated the structure of inductive coupler and its magnetic coupling to increase the transmission coefficient for power line communication. A Rogowski coil, which is an air-cored inductive coupler, and a magnetic cored coupler were fabricated to analyze the transmission coefficient for different coupler parameters. This paper proposes the impedance matching method using lumped elements and an impedance transformer to increase the transmission coefficient. In the experiment, the transmission coefficient of the proposed system was increased in both narrowband and broadband cases, and a trade-off between the transmission coefficient and the bandwidth was shown. This method will be useful for the further study of impedance matching with the load variation.

• Journal of Ocean Engineering and Technology
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• v.23 no.3
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• pp.6-13
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• 2009

Based on the boundary element method, the motion responses and transmission coefficients of a moored floating breakwater were investigated in oblique waves. To satisfy the outgoing radiation condition in the far field, the fluid domain was divided into inner and outer regions. The complete solution could be obtained by applying the matching conditions between the eigenfunction-based outer solution and BEM-based inner solution. Using the developed predictive tools, the wave exciting forces, added mass, damping coefficients, motion responses, and transmission coefficients were assessed for various combinations of breakwater configuration, wave heading, mooring cables properties, and wave characteristics. It was found that the transmission coefficient for a moored floating breakwater was closely dependent on the motion responses, which were greatly amplified at the resonant frequencies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.770-773
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• 2004

The transmission loss coefficient is very important acoustic property in parallel with absorption and acoustic impedance categorizing the acoustical materials, which can control the acoustical problems. At the same time, the transmission loss coefficient is a key parameter to choose the optimum material for the analysis of acoustical characteristics of material using SEA(Statistical Energy Analysis). In this paper, the acoustic transmission loss measurement system using 4-microphone TL tube is applied to the exhaust system, which is one of the most important acoustic control parameters in a car, based on the idea calculating the full transfer matrix. The theoretical background and measurement system are introduced, and finally the measurement results are verified.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.4
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• pp.45-51
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• 2003

The reflection and transmission of submerged breakwater with trapezoidal type are computed numerically using boundary element method. The analysis method is based on the wave pressure function with the contlnuit? in the analytical region including fluid and porous structures. Wane motion within the porous structures is simulated by introducing the linear dissipation coefficient and added mass coefficient. The results indicate that transmission and reflection coefficient are determined due to the change of slope of submerged breakwater with trapezoidal type.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.1
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• pp.52-58
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• 2019

Due to icing and snow, power transmission lines have asymmetric cross sections, and their motion becomes unstable. At this time, the vibration caused by the wind is called galloping. If galloping is continuous, short circuits or ground faults may occur. It is possible to prevent galloping by installing spacers between transmission lines. In this study, the transmission line is modeled as a mass-spring-damper system by using RecurDyn. To analyze the dynamic behavior of the transmission line, the damping coefficient is derived from the free vibration test of the transmission line and Rayleigh damping theory. The drag and lift coefficient for modeling the wind load are calculated from the flow analysis by using ANSYS Fluent. Galloping simulations according to spacer stiffness and interval are carried out. It is found that when the stiffness is 100 N/m and the interval around the support is dense, the galloping phenomenon is reduced the most.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.9
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• pp.1073-1078
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• 2012

This paper presented the extraction solution for the coupling coefficient at the magnetically coupled wireless power transmission(WPT) system through the analysis of its equivalent circuit considering the loss. The conventional extraction solution using coupled mode theory is generalized employing the extracted solution considering the load resistance. Consequently, the measuring process of extracting coupling coefficient becomes convenient since the even/odd mode analysis is not necessary. Furthermore, the coupling coefficient obtained from the induced extraction method was in excellent agreement with the coupling coefficient obtained using the ratio of magnetic flux passing through the two loops. The extraction of the accurate coupling coefficient at the magnetically coupled WPT is an essential work to analyze and optimize the WPT system.

• Journal of Korean Society of Steel Construction
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• v.23 no.1
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• pp.73-81
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• 2011

The wind force coefficient of a transmission tower frame shows several characteristics when the section shape, solidity ratio, and wind direction angle are changed. In this study, the wind force characteristics of a transmission tower frame with a basic structure were evaluated using different solidity ratios and wind direction angles in a wind tunnel test. According to the solidity ratio, the size of the structure and the rectangular-frame model of the transmission tower were changed by adding a two-dimensional (2D) or three-dimensional (3D) structure. The transmission tower's rectangular frame was tested by changing the wind direction angle of the 2D-type structure from 0 to $90^{\circ}$ and by changing the wind direction angle of the 3D-type structure from 0 to $45^{\circ}$ Based on the results that were obtained, it can be concluded that the wind force coefficient of a transmission tower frame can be used as preliminary data in deciding the transmission tower's wind load.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1599-1601
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• 2000

To study invar alloy as a core material for large ampacity over-head transmission line which have high strength and low thermal expansion coefficient simultaneously, thermal expansion coefficient, physical properties and hardness of Fe-Ni-Co-xC alloy have been studied. It is necessary that invar alloy possess low thermal expansion coefficient and high strength for increased capacity over-head transmission line. In this paper we tried to find out the effect of carbon addition related with mechanical and physical properties. It was found that the thermal expansion coefficient and hardness were increased with carbon addition for whole composition range but the saturation magnetization was decreased except for the range of 0.1$\sim$0.4%C.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.51-55
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• 2007

In this paper Statistical Energy Analysis has been considered to predict high frequency air borne interior noise. Dash panel Insulation is major part to reduce engine excitation noise. Transmission loss and absorption coefficient are considered to predict dash insulation performance. Transmission lose is derived from coupling loss factor and absorption coefficient is derived from internal damping loss factor. Material Biot properties were used to calculate each loss factors. Insulation geometry thickness distribution was hard to measure, so FeGate software was used to calculate thickness map from CAD drawing. Each predicted transmission losses between conventional insulation and light weight insulation were compared with SEA. Transmission loss measurement was performed to validate each prediction result, and it showed good correlation between prediction and measurement. Finally interior noise prediction was performed and result showed light weight insulation system can reduce 40% weight to keep similar performance with conventional insulation system, even though light weigh insulation system has lower sound transmission loss and higher absorption coefficient than conventional system.

• Journal of Ocean Engineering and Technology
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• v.27 no.6
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• pp.90-94
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• 2013

This paper reports the results obtained for there flection and transmission coefficients on rubble mound breakwaters in Busan Yacht Harbor. A2D physical model test was conducted in the wave flume at the Coastal Engineering Research Laboratory at Pusan National University, Busan, South Korea. In this study, physical model tests were completed to further our understanding of the hydrodynamic processes that surround a rubble mound structure subjected to irregular waves. In particular, the reflection and transmission coefficients, as well as the spectrum transformation, were analyzed. This analysis suggests that with an increase in wave height around a rubble mound, the reflection coefficient drastically increases at each water level (HHW or MSL or LLW). Moreover, when the water level changes from HHW to LLW, the reflection coefficient is suddenly reduced. A further result of the analysis is that the transmission coefficient strongly drops away from the rear of the structure. Finally, in regard to the rubble mound breakwater in Busan Yacht Harbor, a consideration of the reflection and transmission coefficients plays an important role in the design.