• 한국산학기술학회논문지
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• 제12권11호
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• pp.5172-5177
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• 2011

본 논문은 박막 실리콘 태양전지에 적용되는 반사방지 또는 고반사 코팅 기술에 관한 연구이다. 태양광 흡수율을 개선하기 위하여 박막 실리콘 태양전지의 앞면에는 반사를 줄이는 반사방지막 기술이 필요하며, 뒷면에는 반대로 반사를 높이는 고반사 기술이 필요하다. 반사방지막 기술에서 단층의 구조에서는 코팅의 두께에 따라 반사율이 틀려지고, 적절한 범위에서 두께를 제어하면 낮은 반사율을 얻을 수 있다. 대칭형태의 다층의 구조에서는 단층구조에 비해서 넓은 파장대에 걸쳐서 낮은 반사율을 얻을 수 있다. 또한 뒷면에 적용되는 고반사막 기술에서는 높은 굴절율을 갖는 매질과 낮은 굴절율을 갖는 매질을 대칭 구조로 구성하여 계산한 결과 높은 반사율을 얻을 수 있다는 것을 확인하였다.

• Steel and Composite Structures
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• 제21권2호
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• pp.249-266
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• 2016

The interest of this article lies in the proposition of using bionic method to develop a new sound absorber and analyze the efficient of this absorber in a ski cabin. Inspired by the coupling absorption structure of the skin and feather of a typical silent flying bird - owl, a bionic coupling multi-layer structure model is developed, which is composed of a micro-silt plate, porous fibrous material and a flexible micro-perforated membrane backed with airspace. The finite element simulation method with ACTRAN is applied to calculate the acoustic performance of the multi-layer absorber, the vibration modal of the ski cabin and the sound pressure level (SPL) near the skier's ears before and after pasting the absorber at the flour carpet and seats in the cabin. As expected, the SPL near the ears was significantly reduced after adding sound-absorbing material. Among them, the model 2 and model 5 showed the best sound absorption efficiency and the SPL almost reduced 5 dB. Moreover, it was most effctive for the SPL reduction with full admittance configuration at both the carpet and the seats, and the carpet contribution seems to be predominant.

• 한국실내디자인학회논문집
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• 제14권3호
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• pp.191-198
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• 2005

The present study is a preliminary research improving the dwelling quality of one-room type multi-family housings around the university campus. The purpose of the study is to investigate the present condition of Indoor noise level using · residents' responses and field measurements. The respondents are 104 residents living in one-room type multi-family housings. The field measurements on equivalent noise level of indoor and outdoor were carried out in 6 subject house units during the $26th\~28th$ of November 2002. The results are as follows. 1) The residents show relatively non-positive responses at evening and night on the present condition of indoor noise. 2) They answer 'living equipment foise' and 'water hammer' as major types of indoor noise of house unit. 3) Outdoor noise levels, basic factor of noise environment in 6 subject buildings were distributed $52.8\~65.3dB(A)Leq_{5min}$ and were inappropriate to the standard for environmental noise, $55 dB(A)Leq_{5min}$. 4) Indoor noise levels of subject house units were measured as $27.5\~63.5dB(A)Leq_{5min}$, the average of each house unit except one house unit was higher than the level feeling as noise, 40dB(A). 5) It was found that the differences of indoor noise levels between subject house units were caused by 'residents' living noise', 'living equipment noise', 'water hammer', and 'walking and talking noise in stairs and corridors'. 6) Therefore, it is required to plan for improving the quality of noise environment in one-room type multi-family housing around the campus. For example, soundproof construction (including double window with pair glass and balcony), outdoor garden with trees and water for increasing natural sound, interior materials with sound absorbing power to absorb living noise, soundproof pipe or double surface pipe for decreasing 'water hammer', and noiseproof floors, etc. are required.

• 한국재료학회지
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• 제10권2호
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• pp.171-174
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• 2000

본 연구에서는 실리콘 wafer위에 sputtering방법으로 진공증착된 CoNbZr 비정질 박막을 Nd:YAG 레이저로 식각하기 위한 실험을 했는데, 금속의 경우 표면에서 빛의 반사율이 매우 크기 때문에 파장이 $1.06{\mu\textrm{m}}$인 Nd:YAG 레이저의 에너지를 흡수하는 것이 매우 어려우므로 식각이 거의 이루어지지 않았다. 그래서 이러한 문제를 해결하기 위한 새로운 시도로서 본 연구에서는 빛의 흡수율이 좋은 검은색의 polymer막을 금속박막의 표면에 도포하고 이 polymer막 위에 레이저를 조사해서 금속박막의 식각하는 실험을 실시하였다. 기존의 방법으로는 laser power가 332W나 되는데도 식각이 거의 일어나지 않았지만 본 연구의 방법을 이용했을 때는 laser power가 114W로 1/3정도 밖에 안 되는데도 레이저 식각이 비교적 양호하게 이루어졌다. 이는 검은색의 polymer층이 Nd:YAG 레이저 에너지의 흡수 및 전달 층의 역할을 하기 때문인 것으로 생각된다.

• 해양환경안전학회지
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• 제20권5호
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• pp.593-600
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• 2014

본 연구에서는 첨단 함형에 레이더 반사면적 감소기술을 적용하고 특성을 분석하였다. 특히, 레이더 반사면적에 영향을 주는 요소, 레이더 반사면적을 최소화 하는 방안, 표적의 특수 재질 물성에 대한 레이더 반사면적의 변화 영향을 고찰하였다. DDG-1000 type 첨단 함형의 함정 고각별 레이더 반사면적 해석 결과 고각이 10도 높아짐에 따라서 RCS 평균값이 23.91 dBsm 증가하는 것을 확인하였다. 또한, 함정 상부구조물의 경사각이 6도 증가함에 따라서 RCS 평균값이 1.27 dBsm 감소하는 것을 확인하였다. 마지막으로 상부구조물 앞면과 뒷면에 전파흡수체를 부착한 경우 RCS 평균값이 2.27 dBsm 감소 하는 것을 확인하였다.

• 설비공학논문집
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• 제28권6호
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• pp.224-231
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• 2016

When aiming to reduce the low frequency noise of a subway guest room through sound absorbing treatment methods inside the wall of a tunnel the resonator is often more effective than a porous sound absorbing material. Therefore, the perforated panel type resonator embedded with a perforated panel is proposed. The perforated panel is installed in the neck, which is then extended into the resonator cavity so that it can ensure useful volume. The absorption performance of the perforated panel type of resonator is obtained by acoustic analysis and experiment. The analytical results are in good agreement with the experimental results. In the case of multiple perforated panel type resonators, as the number of perforated panels increase, the 1st resonance frequency is moved to a low frequency band and sound absorption bandwidth is extended on the whole. In order to obtain excellent absorption performance, the impedance matching between multi-panels should be considered. When the perforated panel in the resonator is combined with a porous material, the absorption performance is highly enhanced in the anti-resonance and high frequency range. In case of the resonator inserted with perforated panels of 2, the 2nd resonance frequency is shifted to a low frequency band in proportion to the distance between perforated panels.

• 한국전산유체공학회지
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• 제17권4호
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• pp.56-68
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• 2012

Nowadays, Unmanned Combat Air Vehicle(UCAV) has become an important aircraft system for the national defense. For its efficiency and survivability, shape optimization of UCAV is an essential part of its design process. In this paper, shape optimization of UCAV was processed for aerodynamic performance improvement and Radar Cross Section(RCS) reduction using Multi Objective Genetic Algorithm(MOGA). Lift and induced drag, friction drag, RCS were calculated using panel method, boundary layer theory, Physical Optics(PO) approximation respectively. In particular, calculation applied Radar Absorbing Material(RAM) was performed for the additional RCS reduction. Results are indicated that shape optimization is performed well for improving aerodynamic performance, reducing RCS. Further study will be performed with higher fidelity tools and consider other design segments including structure.

• 한국기계가공학회지
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• 제4권4호
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• pp.34-38
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• 2005

This is a widespread requirement for low cost lightweight thermal imaging sensors for both military and civilian applications. Today, a large number of uncooled infrared detector developments are under progress due to the availability of silicon technology that enables realization of low cost IR sensor. System prices are continuing to drop, and swelling production volume will soon drive process substantially lower. The feasibility of micromechanical optical and infrared (IR) detection using microcantilevers is demonstrated. Microcantilevers provide a simple Structurefor developing single- and multi-element sensors for visible and infrared radiation that are smaller, more sensitive and lower in cost than quantum or thermal detectors. Microcantilevers coated with a heat absorbing layer undergo bending due to the differential stress originating from the bimetallic effect. This paper reports a micromachined silicon uncooled thermal imager intended for applications in automated process control. This paper presents the design, fabrication, and the behavior of cantilever for thermomechanical sensing.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1202-1204
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• 2006

Various types of perforated sheets have been applied on the surface of porous absorptive materials in order to protect dust and to enhance interior design. This study examines experimentally influences on absorptive characteristics according to the shape of perforation which includes rectangular and resonator type as well as circular holes. The measured results shows that the resonance frequency can be changed by the shape of perforation as well as the eccentricity of holes.

• 한국태양에너지학회 논문집
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• 제29권3호
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• pp.28-36
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• 2009

The majority of fixed shading devices are installed in the exterior of a building in order to dissipate the heat absorbing from the sun and to prevent the direct sunlight. In designing external shading devices for windows, many requirements must be considered simultaneously; solar geometry, optimum energy performance, multi-purpose usage and design factors etc.. In order Lo satisfy these requirements, we suggests the folding shading device and its optimum design methodology. Also we analyzed the thermal performance using the IES_VE program according to various operating modes and compared with existing shading devices. The results show that proposed device reduce about $1.90{\sim}22.40%$ in cooling load and about $1.09{\sim}24.22%$ in heating load in comparison with existing ones.