• 한국군사과학기술학회지
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• 제25권3호
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• pp.251-258
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• 2022

Infrared stealth technology used in aircraft is applied to reduce the infrared signal by controlling surface temperature and emissivity using internal heat sink, low emissivity material or metamaterial. However, there is one part of the aircraft where the use of this technology is limited, and that is the radome. Especially, radome should have transmittance for the specific radio frequency, therefore, common stealth technology such as emissivity control surfaces cannot be applied to radome surface. In this study, we developed metal nano-coating for infrared stealth which is applicable to radome surface. We designed slot-type pattern for frequency selective transmission in X-band, and also controlled thickness of metal nano-coating for long wavelength infrared emissivity control. As a result, our infrared stealth surface for radome has 93.2 % transmittance in X-band and various infrared emissivities from 0.17 to 0.57 according to nano-coatings thickness. Also, we analyzed infrared signature of radome through numerical simulation, and finally reduced contrast radiant intensity by 97.57 % compared to polyurethane surface.

• 한국터널지하공간학회 논문집
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• 제23권6호
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• pp.535-547
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• 2021

국내에서는 수소경제 활성화 정책을 수립하고 수소사회 실현을 위해 수소 인프라 및 수소차 보급 확대를 계획 하고 있다. 이에 따라 수소차의 보급이 급속도로 이루어질 것으로 예상되며, 동시에 수소차의 사고에 대응하기 위한 대책의 확립이 요구되고 있다. 본 연구에서는 수소차에 의해서 발생되는 수소 제트화염이 터널 내부 벽체에 미치는 영향과 내부 복사열 특성 분석을 위해 실험적 연구를 수행하였다. 실험은 수소차에서 발생되는 조건과 동일하게 하기 위해 분사압력을 700 bar로 설정하고, 분사노즐 직경은 1.8 mm로 설정하였다. 또한, 일반 터널에 적용되고 있는 콘크리트 압축강도 40 MPa의 터널 내화 시험체를 제작하고 제트화염 분사노즐과 시험체간의 이격거리에 따른 영향을 검토하였다. 분사노즐과 터널 내화시험체의 이격거리를 변수로 하여 2 m와 4 m에 대해 결과를 분석하였다. 그 결과로부터 시험체 내부 최대 온도는 1,349.9℃ (이격거리 2 m)가 측정되었고, 제트화염 주위 복사열은 최대 39.16 kW/m²까지 나타났다.

• 한국생산제조학회지
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• 제18권3호
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• pp.285-293
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• 2009

Thermal infrared cameras have been conducted actively in various application areas, such as military, medical service, industries and cars. Because of their characteristic of sensing the radiant heat emitted from subjects in the range of long-wavelength($3{\sim}5{\mu}m$ or $8{\sim}12{\mu}m$), and of materializing a vision system, when general optics materials are used, they don't react to the light in the range of long-wavelength, and can't display their optic functions. Therefore, the materials with the feature of higher refractive index, reacting to the range of long-wavelength, are to be used. The kinds of materials with the characteristic of higher refractive index are limited, and their features are close to those of metals. Because of these metallic features, the existing producing method of optical systems were direct manufacturing method using grinding method or CAD/CAM, which put limit on productivity and made it difficult to properly cope with the increasing demand of markets. GASIR, a material, which can be molded easily, was selected among infrared ray optics materials in this study, and the optical system was designed with two Aspheric lenses. Because the lenses are molded in the environment of high temperature and high pressure, they require a special metallic pattern. The metallic pattern was produced with materials with ultra hardness that can stand high temperature and high pressure. As for the lens mold, GMP(Glass Molding Press) of the linear transfer method was used in order to improve the productivity of optical systems for thermal infrared cameras, which was the goal of this paper.

• 한국의류학회지
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• 제34권4호
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• pp.553-562
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• 2010

This survey investigates the conditions of summer working uniforms for contracted foodservice workers. The data were obtained from 67 workers through in-depth interviews (July 2005~October 2005). The results of study are as follows: The working environment changed to menu and cooking method (air temperature $28\sim37^{\circ}C$, humidity 72~86 %RH, radiant temperature $27\sim37^{\circ}C$, air velocity 0.14~0.37m/sec). They answered that the working environment has high temperatures, humidity, excessive noise, and liability to slide. The typical accidents were burns, cuts, slide, and ligament injuries in the workplace. Work duties consisted of cooking, serving food, washing, and cleaning up leftover food. All the employees carried out multi tasks. The primary working postures and motions were standing, crouching, and lifting. The female workers usually wore underwear (panty and brassiere), upper and lower work wear, aprons, waterproof-aprons, cotton-gloves, rubber-gloves, socks, and rubber-boots. The satisfaction of the uniform was relatively low for trousers and waterproof-aprons. The answer about the fit was generally "comfortable." They answered "back," "chest," and "head" were wet with perspiration during work. The uncomfortable parts were the crotch and neck. Questions concerning their satisfaction with the material of uniforms indicated a high rate of dissatisfaction, particularly for ventilation and absorbency. In case of the colors of the working uniform, workers preferred white color for the upper part, and black color for the lower part.

• 한국환경보건학회지
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• 제43권3호
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• pp.214-222
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• 2017

Objectives: A hospital is a complex building that serves many different purposes. The indoor environment in a hospital plays a major role in patient well-being and the work efficiency of the hospital staff. This study was conducted to evaluate overall comfort in two major hospitals over the course of one year. Methods: Various indoor environmental conditions were measured in two general hospitals for one year (April 2014 to April 2015). Monitoring alternated between the hospitals at one month per respective monitoring session. The indoor air temperature, relative humidity (RH), mean radiant temperature and air velocity were measured in order to calculate the predicted mean vote (PMV). Carbon dioxide concentration, noise level and illumination level were concurrently measured and applied to the overall IEQ acceptance model for the hospitals (IEQh). Results: The IEQh at the two general hospitals was different at five spaces within a building. The IEQh for summer and winter were significantly different. Real-time IEQh demonstrated that indoor comfort was affected by the hospital's operating hours due to operation of the HVAC system. The percentage of indoor comfort in the hospitals was higher using PMV than IEQh. Conclusion: IEQh in the hospitals was different at locations with different purposes. Indoor comfort assessment using IEQh was stricter than with PMV. Additional research is needed in order to optimize the IEQh model.

• 한국전자통신학회논문지
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• 제9권12호
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• pp.1435-1440
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• 2014

본 논문에서는 13.2W급 COB LED의 공랭식 방열을 위해 열전소자를 이용하여 열적 특성을 분석하였다. 기존 방식과의 방열 성능을 비교 분석하기 위하여 Heat Sink를 설계 및 제작 하였고 실험은 100분간 COB LED를 구동시켜 접촉식 온도계를 통하여 온도 분포를 측정하였다. 접합부의 온도 측정 결과 열전소자를 사용하지 않는 방식에서는 약 $75^{\circ}C$로 나타났고, 열전소자에 0.8A의 전류를 인가하여 구동하였을 때 $57^{\circ}C$로 열 응집현상이 가장 심한 COB LED 접합부분의 열은 기존의 방식보다 약 31% 감소됨을 확인하였다.

• 한국화재소방학회논문지
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• 제28권6호
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• pp.22-27
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• 2014

본 연구에서는 Fuel bed를 이용한 실험을 통하여 지표화 확산에 의한 온도 분포, 화염 높이, 복사열, 확산속도 등을 측정하였다. 실험 변수로는 수종, 풍속 및 경사도 등을 사용하였다. 수종으로는 침엽수종인 소나무 낙엽과 활엽수종인 굴참나무 낙엽을 사용하였다. 풍속은 터널식 방 구조에서 간이풍속 장치를 이용하여 1 m/s, 3 m/s, 5 m/s 풍속을 조절하여 실험하였다. 경사도는 Fuel bed의 기울기를 $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$로 변화시켜 가며 조절하였다. 온도 분포 및 확산속도를 측정하기 위하여 K-type 1.6 mm 열전대를 35개를 격자모양으로 배치하였다. 측정을 위하여 복사열량계를 사용하였으며 이외에도 비디오 카메라 및 열화상 카메라를 사용하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.193-193
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• 2011

To obtain ceramic films, the sol-gel coating technique has been broadly used with heat treatment, but crack formation tend to occur during heat treatment in thick sol-gel films. We prepared PZT thin films by sol-gel method with single-step spin coating process. The PZT solution have been synthesized using lead acetate ($Pb(CH_3COO)_2$), zirconium acetylacetonate ($Zr(OC_3H_7^n)_4$), and titanium diisopropoxide bis(acetylacetonate) 75wt% in isopropanol ($Ti(OC_3H_7^i)_2(OC_3H_7^n)_2$) as starting materials and n-propanol was selected as a solvent. The poly(vynilpyrrolidone) (PVP) was added with 0, 0.25, 0.5, 0.75, and 1 molar ratios to control viscosity of solution. We investigated influence of the viscosity on thickness, microstructure, and electrical properties of final PZT films. Thermo-gravimetric analysis and differential scanning calorimeter (TGA/DSC) was carried out from room temperature to $800^{\circ}C$ in order to measure pyrolysis temperature. Structural characteristics were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Ferroelectric and dielectric properties were measured by RT66A (Radiant) and impedance analyzer (Agilent), respectively. The thicknesses of PZT films depended on incorporation of an excess amount of PVP. Finally, we obtained PZT films of good quality without crack formation via single-step spin coating.

• 한국재료학회지
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• 제33권10호
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• pp.414-421
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• 2023

Infrared radiation (IR) refers to the region of the electromagnetic radiation spectrum where wavelengths range from about 700 nm to 1 mm. Any object with a temperature above absolute zero (0 K) radiates in the infrared region, and a material that transmits radiant energy in the range of 0.74 to 1.4 um is referred to as a near-infrared optical material. Germanate-based glass is attracting attention as a glass material for infrared optical lenses because of its simple manufacturing process. With the recent development of the glass molding press (GMP) process, thermal imaging cameras using oxide-based infrared lenses can be easily mass-produced, expanding their uses. To improve the mechanical and optical properties of commercial materials consisting of ternary systems, germanate-based heavy metal oxide glasses were prepared using a melt-cooling method. The fabricated samples were evaluated for thermal, structural, and optical properties using DSC, XRD, and XRF, respectively. To derive a composition with high glass stability for lens applications, ZnO and Sb₂O₃ were substituted at 0, 1, 2, 3, and 4 mol%. The glass with 1 mol% added Sb₂O₃ was confirmed to have the optimal conditions, with an optical transmittance of 80 % or more, a glass transition temperature of 660 ℃, a refractive index of 1.810, and a Vickers hardness of 558. The possibility of its application as an alternative infrared lens material to existing commercial materials capable of GMP processing was confirmed.

• Ecology and Resilient Infrastructure
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• 제7권4호
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• pp.227-237
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• 2020

도시지역의 여름철 밤 시간대 열환경을 알아보기 위해, 토지피복 대분류에 따라 10개의 도시기후지역 지점에서 미기후 자료를 측정하여 인간 열환경지수를 분석하여 보았다. 미기후 요소 비교 분석 결과, 그린인프라 지역이 그레이인프라 지역보다 기온에서는 평균 1.6℃ 최대 2.4℃ 낮은 결과를 보였으며, 상대습도에서는 반대로 그린인프라 지역이 평균 9.0% 최대 15.0% 높은 결과를 보였다. 풍속에서는 그린인프라 지역과 그레이인프라 지역에서 차이가 거의 없는 것으로 나타났으며, 수목의 영향으로 가장 낮은 풍속을 보인 산림지점을 제외하고는 모든 지점에서 유의성이 없는 것으로 나타나, 건물이나 수목의 높이에 의해 결정되는 표면거칠기 뿐만 아니라 지역풍의 영향이 풍속을 결정하는 주 요인인 것으로 보인다. 평균복사온도에서는 수목의 영향으로 산림지역이 가장 높은 값을 보였으며, 산림지역을 제외하면 그린인프라 지역이 그레이인프라 지역에 비해 평균 5.5℃의 저감 효과를 보였다. 평균복사온도를 결정하는 주 요인으로는 하늘시계지수라고 할 수 있다. 인간 열환경지수 분석에서는 그린인프라 지역은 거의 덥지도 춥지도 않는 '중립'의 열지각 단계를 나타내었으며, 그레이인프라 지역은 그것보다 한 단계 높은 '약간 따뜻함'의 단계를 나타내었다. 가장 높게 나온 산림지역을 제외하면, 그린인프라 지역이 그레이인프라 지역에 비해 3.2℃ 저감 효과를 보여 1/2 단계의 인간 열환경 개선 효과가 있는 것으로 나타났다.