• 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.

• Proceedings of the Materials Research Society of Korea Conference
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• 1992.05a
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• pp.87-88
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• 1992

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.11a
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• pp.180-180
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• 1996

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.11
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• pp.2206-2212
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• 2017

When it comes to naval surface warfare, the probability of detection is an important factor in survivability and the Radar Cross Section(RCS) is a major parameter. In this paper, the RCS reduction technology of the Radar Absorbing Material(RAM) method is carried out for the general frequency range for naval warfare. We set the analysis model with the simplified ship model and the wide band metamaterial which is high-tech radar absorbing materials is selected for the RAM method. The modeling of the wide band metamaterial composed of an MIK surface which has the wide band resonant properties and flexible substance and the electromagnetic absorptions and reflections of the wide band metamaterial has been simulated to explore the performance. Also, the wide band metamaterial is compared with the paint absorber to analyze RCS reduction in terms of RCS values.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.198.2-198.2
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• 2007

• Textile Coloration and Finishing
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• v.22 no.3
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• pp.264-271
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• 2010

The purpose of this study was to investigate performance evaluation of absorbing and fast-drying fabric after washing. In the comparison of absorption and fast-drying properties, there was slight difference among the materials depending on thickness, weight, and fabric structure. Absorption speed of the materials depended on the frequency of washing which might be caused by modification of fabric structure or composition fiber due to friction during washing. The ability of fast-drying of the materials was gradually decreased with the increase of washing frequency, which might be caused by fatigue accumulation on inner fiber and structural change or destruction with friction during washing.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.12a
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• pp.93-94
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• 2004

• Magazine of the Korea Concrete Institute
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• v.20 no.6
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• pp.70-74
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• 2008

• Journal of Forest and Environmental Science
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• v.40 no.2
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• pp.90-98
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• 2024

This study analyzes the characteristics of sound-absorbing materials made from forest by-products of the deciduous tree species Zelkova serrata (Z. serrata) by evaluating their sound absorption performance. Accordingly, sound-absorbing materials with varying sample thicknesses, leaf sizes, and drying conditions were fabricated. The sound absorption properties were measured using the impedance tube method via middle-type measurement tube (100 Hz-3,200 Hz). The sound absorption properties were evaluated using the average sound absorption coefficient (ASAC), which was calculated from the measured sound absorption coefficients at 250 Hz, 500 Hz, 1,000 Hz, and 2,000 Hz. The ASAC value significantly improved as the leaf size increased to 0.5×0.5 cm², 1.0×1.0 cm², and 2.0×2.0 cm². The ASAC values under the two drying conditions were similar. There was no significant difference in ASAC according to the leaf size under the air-dried leaf condition, with a thickness of 2.50 cm. The highest ASAC value according to the sound-absorbing material thickness was 0.47 at a thickness of 2.50 cm and leaf size of 2.0×2.0 cm² under the air-dried leaf condition. In addition, the variation in ASAC was 0.23, indicating that the sound absorption performance according to leaf thickness was more significant than the difference in absorption properties according to leaf size. A sound absorption coefficient (SAC) of 0.4 or higher was observed across the measurable frequency band (100 Hz-3,200 Hz). Furthermore, the SAC values with respect to leaf size and thickness were close to 1 in the high-frequency range above 2,000 Hz. Therefore, it is considered that sound-absorbing materials using Z. serrata leaves are advantageous in the field of absorbing noise in a high-frequency band of 2,000 Hz or more, and it is better to manufacture a thickness of 2.50 and 2.0×2.0 cm².

• Proceedings of the KSR Conference
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• 2002.05a
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• pp.603-608
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• 2002

Sound absorbing materials are applied to the exposed surfaces of curved subway tunnel for the reduction of curving noise level. Before the treatment, acoustical engineering simulation is performed to predict the noise level reduction for different kinds and amounts of absorbing material. The principle of geometrical acoustics is utilized to Peform the simulation efficiently and accurately. The noise levels of the inside and outside of running car body are measured to find the noise level reduction. The average noise level reduction of 8 ㏈ has been attained. It has been shown that the simulated results are comparable to the measured ones.