• Journal of the Korean Wood Science and Technology
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• 제48권1호
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• pp.32-40
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• 2020

While the utilization of wood as a raw material in related industries has been increasing with the population increasing, the availability of wood from natural forests has continued to decline. An alternative to this situation is the manufacture of particleboard from non-wood lignocellulose materials through the modification of sandwich particleboard (SPb) using bamboo strands as reinforcement. In this study, strandsof belangke bamboo (Gigantochloa pruriens W) and tali bamboo (Gigantochloa apus) were utilized. The non-wood particles included sugar palm fibers, cornstalk, and sugarcane bagasse. The board was made in a three-layer composition of the face, back, and core in a ratio of 1: 2: 1. The binder used was 8% isocyanate resin. The sheet was pressed at a temperature of 160℃ for 5 min under a pressure of 3.0 N/㎟. Testing included physical and mechanical properties based on the JIS A 5908 (2003) standard, while acoustic testing was based on ISO 11654 (1997) standards. The results showed that using bamboo strands as reinforcement has an effect on the mechanical and physical properties of SPb. Almost all the types of boards met the JIS A 5908 (2003) standards, with the exception of thickness swelling (TS) and internal bond (IB) parameters. Based on the thickness swelling parameter, the C-type board exhibited the best properties. Overall, the B-type board thatused a belangke bamboo strand for the surface and sugarcane bagasse as the core underwent the best treatment. Based on the acoustical parameter, boards using a tali bamboo strand for the surface and sugar palm fiber as the core (E-type board) exhibited good sound absorption properties.

• 생물환경조절학회지
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• 제20권1호
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• pp.33-39
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• 2011

시설재배 딸기를 위한 생력적이고 환경친화적인 순환식 수경재배기술을 확립하기 위하여 고형배지 종류별로 딸기의 무기이온 흡수 특성을 조사하였다. 톱밥배지를 제외한 나머지 세 종류의 배지에서는 대체적으로 많은 양의 질산태질소의 흡수를 나타내었는데, 펄라이트배지와 입상양면배지 보다는 코코피트배지에서 약간 높은 흡수농도를 나타내었다. 인은 톱밥배지를 제외한 세 종류의 배지에서는 초기에는 $5me{\cdot}L^{-1}$의 높은 흡수농도를 나타내었으며 생육이 진행됨에 따라 점차 감소하여 $3me{\cdot}L^{-1}$ 정도의 흡수량을 나타내었는데, 이것은 비교적 높은 농도로서 추후 검토를 할 필요가 있을 것으로 생각되었다. 그러나 톱밥배지에서는 3월 중순까지 인의 흡수가 거의 없는 것으로 나타났다. 칼륨의 흡수농도는 톱밥배지를 제외하고는 세 배지 모두 비슷한 흡수량을 나타내었는데 생육초기에는 비교적 높은 흡수량을 나타내었지만 점차적으로 감소하여 $4me{\cdot}L^{-1}$ 전후의 흡수량을 나타내었다. 칼슘의 흡수량은 펄라이트배지와 입상암면배지에서는 생육초기에 약간 높은 농도를 나타내기는 하였지만 생육전반에 걸쳐서 $2me{\cdot}L^{-1}$ 정도의 안정적인 흡수양상을 나타내었다. 마그네슘은 코코피트배지에서 생육 전반기에 $3me{\cdot}L^{-1}$ 정도의 높은 흡수농도를 나타내었으며 생육 후반기까지도 다른 배지에 비해서 가장 높은 흡수 농도를 나타내었다. 다음으로는 펄라이트 배지와 입상암면배지 순이었으며 세 배지 모두 마그네슘의 흡수는 대체적으로 $1me{\cdot}L^{-1}$ 정도의 농도를 나타내었다. 본 실험의 결과는 고형배지를 이용한 순환식 딸기 수경재배에서 유용하게 활용될 것으로 생각된다.

• 소음진동
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• 제8권1호
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• pp.146-156
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• 1998

자동차의 폭발적인 증가와 아울러 경부고속전철시대를 맞이함으로 인하여 소음공해는 큰 사회적 문제로 대두되고 있다. 본 연구는 이러한 소음공해에 대한 해결책의 일환으로 효율적인 방음벽을 연구 하는데 그 목적이 있다. 방음벽의 연구는 먼저 반사형 방음벽과 흡음형 방음벽에 대한 소음저감효과 를 산정한 다음, 흡음재료를 사용함으로서 감소되는 소음저감 효과를 산정하는데 큰 의의가 있다. 본 연구결과에 의하면 방음벽의 높이에 비하여 음의 파장이 대체로 짧을 때는 방음벽의 상단부분에 흡음재를 설치하면 방음벽 전체에 흡음재를 설치한 것과 같은 효과가 있다는 결론을 얻었다. 도로교통소음은 평균주파수가 550Hz 이므로 이때 파장은 60cm 정도이다. 방음벽 높이를 4m로 설치했을 때 방음벽 상단에서 60cm 정도만 흡음재를 사용하면 4m전체의 방음벽에 흡음재를 사용한 것과 같은 효과가 있는 것으로 나타났다. 흡음재를 사용한 소음저감의 효과는 점음원이고 수음자의 위치가 $135^{\circ}$ 일 때 평균 8dB(A)정도이고, 선음원일때는 평균 3dB(A)정도의 효과가 있는 것으로 나타났다 이러한 흡음형의 방음벽은 경제적일 뿐만 아니라 방음벽의 높이를 최소한 1m이상 줄일 수 있으므로 국토를 고도로 이용해야 되는 우리 나라의 여건에 대단히 효과적인 방음벽이라 사료된다.

• 한국소음진동공학회논문집
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• 제11권7호
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• pp.253-260
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• 2001

A Study of interior noise reduction in the magelv train is presented. Tarin speed of interest is low such that aero-dynamic noise is negligible and power supply system is a dominant noise source. Based on the measurements of interior noise and acceleration levels during running and zero speed conditions, dominant noise sources are identified. After spectra characteristics of noise sources are investigated several noise reducing methods are studied such as STL increasement of floor panels. sealing. and absorption treatment It is found that the most important noise sources are VVVF inverter and SLM in running condition, whereas air conditioner and DC/DC converter are dominant in zero speed. Sine the major noise sources are under the floor complete sealing and high STL of the floor panel are shown to be the most crucial factors in noise reduction After sound absorbing material, which is polyurethan foam of 50 mm thickness, is thickness, is attached to the downward side of the floor in addition to sealing treatment, the interior noise is reduced by 3~4 dB.

• 설비공학논문집
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• 제19권6호
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• pp.476-484
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• 2007

Recently, in accordance with the buildings are becoming to large-sizes, high-stories, the large scaled facilities and equipments in machine room are quite demanding, and the generated noise volume according to this situation is on increasing. Since such noise is becoming to the object of a serious civil appeal, it is the real situation that a reduction countermeasure against the machine room equipment noise is keenly necessitated. On such viewpoint, this study has recorded, measured the noises which were generated from each individual as same as the whole equipped machines and tools, on the object of the dormitory machine rooms of the 3 colleges that haying mutually different peculiarities, then after grasp-ing their characters and acoustic powers, this research has verified its prediction possibility and the authenticity by comparison the estimated numerical value with the actually measured numerical value through the acoustic simulation. After grasping the prediction possibility in such way, by utilization of the sound absorption material in the machinery room, from the stage of design, the soundproof measures for the noise reduction at machine room could be regulated effectively, and it is also considered that such data would be utilized as the fundamental material for an establishment of the measure for sound insulation.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.6-12
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• 2010

철도소음은 공기역학적 소음, 차륜과 레일의 상호작용에 의한 전동소음과 고가구조음으로 나눌 수 있다. 열차의 속도한계에 의해 재래철도의 주소음원은 전동음이라고 알려져 있으며, 전동음에 대한 많은 연구가 이루어졌다. 또한 전동음을 주소음원으로 하여 철도소음에 대한 예측모델을 제시하고, 철도소음의 전파특징에 대한 연구가 다수 이루어졌다. 또한 근래에는 고가선로에 대한 고가진동음에 대한 연구가 진행되고 있다. 한편, 본 연구에서는 국내 고가철교에 거의 설치되어 있지 않은 방음터널에 대한 효과를 파악하고 앞으로 설치가 예상되는 고가철교 방음터널에 대한 설계 자료를 확보하기 위한 기초연구를 수행하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.606-611
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• 2000

It has been noted that the low frequency absorption coefficient of a porous sample placed in a standing wave tube is affected by the nature of the sample's edge constraint. The edge constraint has the effect of stiffening the solid phase of the sample, which itself can be strongly coupled to the material's fluid phase, and hence the incident sound field, by viscous means at low frequencies. In recent work it has also been shown that such a circumferential constraint causes the low frequency transmission loss of a layer of fibrous material to approach a finite low frequency limit that is proportional to the flow resistance of the layer and which is substantially higher than that of an unconstrained sample of the same material. However, it was also found that the benefit of the circumferential edge constraint was reduced in a transitional frequency range by a shearing resonance of the sample. Here it will be shown that the effect of that resonance can be mitigated or eliminated by adding additional axial and radial constraints running through the sample. It will also be shown that the constraint effect can be modeled closely by using a finite element procedure based on the Biot poroelastic theory. Implications for low frequency barrier design are also discussed.

• 한국정밀공학회지
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• 제19권3호
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• pp.144-151
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• 2002

This work focuses on finding out the noise source and the method of reducing the noise level of LPG(liquefied petroleum gas) fuel injector. The noise of LPG injector in operating condition is due to the impact between valve and valve seat. This study shows that if the revolution of engine is increased, the noise of LPG injector will be more serious but it is not nearly affected by the increment of fuel pressure. The source and transmission paths of noise are identified through the analysis of noise generation mechanism and noise spectrum. The sound absorbing material is tested to verify its efficiency of sound absorption thor the LPG injector. The effect of noise reduction of absorbing material is remarkable when the engine speed is high. Consequently two methods of reducing the noise level are suggested from the identified results. The one is to equip the absorbing material on the outer side of injector and the other is to coat with a soft material or equip a soft ring on the surface of impact.

• 한국정밀공학회지
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• 제29권7호
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• pp.799-804
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• 2012

Recently micro-nano structures has widely been reported to improve the performance of waterproof, heat isolation, sound and light absorption in various fields of electric devices such as mobiles, battery, display and solar panels. A lot of micro-sized holes on the surface of thin film provide excellent sound, or heat, or light transmission efficiency more than solid film and simultaneously nano-sized protrusions around micro hole increase the hydrophobicity of the surface of thin film because of lotus leaf effects as generally known previously. In this paper new rapid fabrication process with 355 nm UV laser ablation was proposed to get micro-nano structures on the surface of thin film, which have only been observed at higher laser fluence. Developed thin micro-nano structured film was also investigated the hydrophobic property by measuring the contact angle and demonstrated the possibility to apply to water droplet separation.

• 정보저장시스템학회논문집
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• 제3권4호
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• pp.196-201
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• 2007

As the demand for the lap-top computer has been increased, most users ask quiet environment to work comfortably. Therefore, noise problems of an ODD are of great interest. For the high speed ODD, the flow induced noise is caused by the turbulent flow[1], which is known to be a major source of overall noise of a slim type ODD. In this study, we introduce a new attempt to reduce the noise level using the concept of Helmholtz resonator[2].The experimental analysis is carried out for several cases at different resonance frequencies and different hole patterns. The results show reductions in the noise level from the acoustic noise absorption point of view.