• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.869-874
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• 2010

A research for the optimal design of microwave absorbing material featuring for the broadband has been conducted to apply to warship. A multilayered structure was suggested using wave absorbing layers and resistance layer to perform high performance in broadband frequencies. For the optimization of the wave absorbing characteristics, the thickness and permittivities of the absorbing layers as well as the surface resistance of the resistant layer were determined using genetic algorithm. The data base of permittivities related to the density of the dielectric materials and loss materials was obtained by the experiments for the dielectric constants of the absorbing layers, furthermore, the results were numerically expressed and used for the optimization.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.421-424
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• 1996

Effects of humidity absorbing deterioration on AC dielectric breakdown characteristics of modified epoxy resin system with SN(succinonitrile) were investigated. As the forced humidity absorbing deterioration proceeded under high temperature and humidify, glass transition temperature increased. The dielectric breakdown strength increased and then decreased at deterioration cycles higher than 2. Not only, the increment of thermal stability but also, the physical detects such as Internal cracks and voids occurred during the humidity absorbing deterioration cycle were the main causes of the change in dielectric properties.

• Advances in concrete construction
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• v.3 no.2
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• pp.103-111
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• 2015

The foam concrete was fabricated by adding the foaming agent which composite ordinary Portland cement with plant and animal protein into cement paste, and the electromagnetic wave absorption properties were studied for the first time as well. The studies showed that the electromagnetic waves can be absorbed by multiple reflections and scattering within the porous material. Thickness and filling ratio have a great influence on the electromagnetic wave absorbing properties in 2-18 GHz of the foam concrete, the greater the thickness, the better the performance of absorption; filling ratio was about 52 vol.%, the absorbing properties achieved the best.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.4
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• pp.365-371
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• 2013

The purpose of this study is to develop a sound absorbing material for indoor which manufactured by a clay and binding material. The seven kind of sound absorbing specimens which sintered through a mold process at high temperature were manufactured for the purpose of testing sound absorption performance. The random and normal sound absorption coefficients were measured for the sintered clay sound absorbing specimens with different particle size, density and mixture ratio. From the experimental results, it was found that its particle size was closely related to the sound absorption performance. It was shown that the sintered clay sound absorbing specimen had the sound absorption properties of a fiber-type or a resonance-type sound absorbing material depending on the particle size.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.387-392
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• 2003

This study is put a focus on the identification of sound characteristics according to the interior configuration of sound absorption material and air gap. Noise barrier is general consists of front perforated panel, air layer, sound absorption material, air gap and back plate. Noise barrier is required to the NRC value of 0.7. The absorbing performance of the noise barrier relies on the opening ratio of the perforated panel and the efficiency of the absorbing material. This study has observed the effect of opening ratio and hole size, the increase of sound absorbing performance by the configurations of sound absorption material and air gap. New designed noise barrier is achieved the acoustical performance of 0.87 the measurement in a reveration room.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.575-580
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• 2013

This study focused on the identification of sound characteristics according to the configuration of sound absorption material and perforated panel dimensions. Noise barriers consist of front perforated panel, sound absorption material and back plate. Noise barriers' acoustic performance should be required to meet the NRC of 0.7. The absorbing performance of the noise barrier relies on the opening ratio of perforated panel and the efficiency of the absorbing material. This study try to find out the possibilities of applications to railway usage.

• Journal of the Korean Wood Science and Technology
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• v.50 no.3
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• pp.179-185
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• 2022

This study investigated the prospect of using peanut shells as an alternative and green sound-absorbing material. The sound-absorption coefficients were determined after filling impedance tubes of 30, 60, and 90 mm in height with peanut shells. The sound-absorption ability increased as the filling height increased, showing noise reduction coefficient (NRCs) of 0.23, 0.43, and 0.54 for the 30-, 60-, and 90-mm heights, respectively. In addition, for sounds greater than 2,000 Hz, the average sound-absorption coefficient of peanut shells in the 60- and 90-mm heights was 0.9. In summary, peanut shells were found to have good sound-absorption properties comparable to or better than those of bamboo, sisal, jute, and wool, and this research suggests that peanut shells may be useful as an environmentally friendly sound-absorbing material.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.6
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• pp.538-544
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• 2000

The laser patterning of sputter-deposited CoNdZr/Cu/CoNbZr multi-layered films had been tried using Nd:YAG laser. However generally it is very difficult to remove metal films because of their high reflectance of the laser on the surfaces. As a counterproposal for this problem authors for the first time tried to deposit energy-absorbing layers on the metal films and then irradiated the laser on the surfaces of energy-absorbing layers. Here the energy-absorbing layers consisted of laser energy-absorbing fine powders and binding polymers. Three kinds of powders for the energy-absorbing layers had been used to see the difference in the pattern formation with the degree of laser energy absorption. They were electrically conductive silver powders insulating BaTiO$_3$powder and semiconducting carbon powder. Remarkable difference in width of the formed pattern and the roughness of pattern edge were observed with the characteristic of the powder for the energy-absorbing layer. The pattern width using carbon paste was about three times larger than that using BaTiO$_3$paste. It was observed that the energy-absorbing layer with carbon was the most effective on this micro-patterning.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.10
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• pp.1196-1203
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• 2011

Statistical optimum methodology of table of orthogonal array, ANOM, ANOVA and RSM are applied to formulate optimum allocation design with design variables. It can be minimized average SPL of control volume, the objective function in closed system by optimal allocated positions of absorbing material. Structural natural frequency and acoustic natural frequency of cavity are analyzed by FEM and BEM in the closed system. Using BEM, average SPL of specific control volume is calculated according to the condition before using absorbing material and after using it. It is shown that noise is reduced by $5.02dB_{RMS}$ by absorbing material located at optimal position and minimum $1.83dB_{RMS}$ and maximum $3.47dB_{RMS}$ by the table of orthogonal array.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.4
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• pp.275-281
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• 2014

This study has been analyzed the sound performance of the noise barriers with respect to the configuration of the front perforated panel geometries and the filled absorption materials. Noise barriers' acoustic performance should be required to meet 0.7 of NRC value at least. The global absorbing performance of the barriers have been investigated by changing the opening ratio of the front perforated panel and the absorbing characteristics of the absorbing material using two microphone method. Therefore, It it possible to obtain to increase acoustic performance of the specific frequency ranges by designing the perforate rates of the front panel and absorbing characteristics of the absorbing materials inside, as well. This study try to find out the possibilities of applying the absorbing noise barrier to railway usage.