• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.437-444
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• 2012

In this paper, the measurement method of the decoupling performance of a underwater decoupling material is studied. First, the simple vibro-acoustic coupled model of a multi-layered underwater decoupling material attached to a plate is analytically derived using impedance transfer matrix. Two test methods are introduced using the theoretical expression of the simple model. One is based on the ratio of the plate vibration and the radiated pressure under impact excitation of the plate. The other is based on the reciprocity theorem and uses the ratio of the incident pressure and the plate vibration under projector excitation in water. Some measurements are carried out according to the test methods using a pulse tube. The test results show the advantages and disadvantages of two methods. It is also shown that the combination of impact and projector excitation methods may be a useful tool to evaluate the performance of a underwater decoupling material.

• Journal of Forest and Environmental Science
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• 제40권2호
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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.

• Journal of the Korean Wood Science and Technology
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• 제48권5호
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• pp.631-640
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• 2020

In this study, the effect of specimen size and layer thickness on the sound absorption of the leaves of two evergreen broad-leaved tree species, Dendropanax morbiferus and Fatsia japonica, was investigated. The specimen sizes of 0.5 × 0.5, 1.0 × 1.0, and 2.0 × 2.0 ㎠ and layer thicknesses of 1.00, 1.75, and 2.50 cm were considered. At the layer thickness of 2.5 cm, the leaf of the D. morbiferus showed no significant difference in sound absorption coefficients (SACs) as the sample size varied, however, a significant change in SACs was recorded in that of the F. japonica. At 1.0-cm thickness, the SACs of the F. japonica leaf varied more remarkably with the sample size. The 2.50-cm-thick F. japonica leaf with the specimen size 0.5 × 0.5 ㎠ exhibited the highest sound absorption effect among all samples investigated.

• 한국환경과학회지
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• 제32권1호
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• pp.25-35
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• 2023

The purpose of this study was to determine the optimal sound absorption conditions by comparing the sound absorption characteristics of fresh and air-dried leaves of Quercus glauca, the main species of evergreen broadleaf trees (EBLT) in southern Korea. The sound absorption coefficients (SACs) obtained under 18 conditions were comparatively analyzed. The SAC of air-dried leaves improved significantly with increasing leaf layer thickness. The highest average SAC in the fresh leaf group was 0.617, which was observed under the condition of a leaf specimen size of 0.5 × 0.5 cm² and a leaf layer thickness of 1.75 cm. In a group of air-dried leaves, this was 0.615 under the condition of a leaf specimen size of 0.5 × 0.5 cm² and a leaf layer thickness of 2.50 cm. The maximum value of SAC for each wavelength was observed under the condition of a leaf layer thickness of 2.50 cm consisting of 0.5 × 0.5 cm² leaf specimens, ranging from 1,400 Hz to 1,500 Hz.

• 한국결정성장학회지
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• 제18권6호
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• pp.264-270
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• 2008

산업현장에서 발생되는 다양한 종류의 폐기물을 이용하여 에코골재를 제조하였다. 에코골재는 폐기물을 분쇄하고 조립성형 후, 로타리 킬른에서 $1125^{\circ}C$/15 min의 조건으로 소성하여 제조되었다. 본 연구진에 의해 제조된 에코골재 K73(Coal bottom ash 70 wt%: Dredged soil 30 wt%)과 K631(Clay 60 wt%: Stone sludge 30 wt%: Spent bleaching clay 10 wt%)을 이용하여 경량 콘크리트 흡음재를 제조하였으며, 비교를 위해 독일에서 수입된 DL(독일산 'L'사 인공경량골재)을 이용한 흡음재 역시 같은 조건으로 제조하였다. 골재의 종류, 물-시멘트비(W/C=20, 25, 30%) 그리고 설계 공극률(20, 25, 30%)의 변화에 따른 흡음특성변화를 관찰하였다. 실험결과, 경량 콘크리트 흡음재의 실제 공극률은 설계 공극률보다 $5{\sim}10%$ 정도 높게 나타났다. 임피던스관을 이용한 흡음재의 흡음계수 측정 결과, K631골재를 이용한 경량 콘크리트 흡음재(W/C=20%, V=25%)가 1000, 3150 Hz에서 각각 0.88의 흡음계수를 나타내었다.

• Journal of the Korean Wood Science and Technology
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• 제49권5호
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• pp.482-490
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• 2021

This research was conducted to analyze the sound absorption effect of air-dried leaves from two evergreen tree species found in Korea's warm-temperate and subtropical regions. As eco-friendly sound absorption materials, Dendropanax morbiferusa, and Fatsia japonica leaves were prepared in three specimen units sizes 0.5 × 0.5 cm², 1.0 × 1.0 cm², and 2.0 × 2.0 cm², and each of them was formed at a thickness of 1.00 cm, 1.75 cm, and 2.50 cm. The measured sound absorption coefficients (SAC) for 18 conditions were comparatively analyzed in this study. The SAC of both tree species was significantly improved by increasing the dried leaf layer thickness. These results showed a more consistent and distinct trend for both tree species under the condition of 0.5 cm² in dried leaf size compared to other leaf specimen sizes. However, as the thickness increased, the difference in sound absorption effect according to the leaf size tends to decrease overall. In the case of D. morbiferus, there was no significant difference in SAC based on leaf size under the condition of 2.5 cm thickness (p < 0.05). The highest mean SAC was found in a 2.5 cm thick condition with a leaf size of 0.5 × 0.5 cm², 0.549 for D. morbiferusa, and 0.594 for F. japonica, respectively.

• 전기전자학회논문지
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• 제18권4호
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• pp.552-558
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• 2014

본 논문에서는 원격 방사선 측정을 위한 ZigBee 원칩형 통신 모듈 설계방법을 제안한다. 제안된 ZigBee 원칩형 통신모듈 설계는 ZigBee 시스템 구성을 위해 일반적으로 사용되는 2개의 칩 제어 프로세서와 ZigBee RF 디바이스로 구성되는 방식을 한 개의 칩 모듈로 설계한다. 원격 방사선 측정을 위한 ZigBee 원칩형 통신 모듈은 무선통신 통합제어부, 센서 및 고전압 발생부, 충전 및 전원회로부, 유선통신부, RF 회로부 및 안테나부 등으로 구성된다. 무선통신 통합제어부는 ZigBee를 위한 무선통신 제어 기능 및 방사선 측정 및 제어를 위한 기능을 수행한다. 센서 및 고전압 발생부는 2차에 걸쳐 500V의 고전압을 생성하여 GM Tube를 통해 감지된 방사선에 대한 펄스를 증폭 필터링 하는 기능을 수행한다. 충전 및 전원회로부는 리튬이온 배터리의 충전 및 원칩 프로세서에 전원을 공급하는 기능을 수행한다. 유선통신부는 PC와의 인터페이스 및 디버깅을 위한 USB 인터페이스 및 원거리 유선 통신이 가능하도록 RS-485/422 인터페이스 기능을 수행한다. RF 회로부 및 안테나부는 칩안테나를 적용할 수 있도록 RLC 수동소자를 적용하여 BALUN 및 안테나 임피던스 매칭 회로를 구성하여 무선통신이 가능하도록 한다. 제안된 원격 방사선 측정을 위한 ZigBee 원칩형 통신 모듈을 설계 실험한 결과, 10m, 100m 구간에서 모두 데이터가 정상적으로 전송되어서 원격 방사선량 측정이 되었음을 확인할 수가 있었다. 또한 낮은 소비전류와 적은 비용으로 원격 방사선량 측정환경을 구축할 수 있었다. 따라서 방사선 측정장치의 선형성 확보 및 장치의 소형화를 통해 안정적인 방사선 측정 및 실시간 모니터링 환경을 구축할 수가 있었다.