• Journal of Radiation Protection and Research
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• 제25권2호
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• pp.109-114
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• 2000

The SI unit of specific absorption rate (SAR) in W/kg in the electromagnetic (EM) field as non-ionizing radiation is exactly same as the SI unit of absorbed dose rate in Gy/s in the ionizing radiation field. The SI unit of both physical quantities can be expressed in $[m^{\cdot}s^{-3}]$. Where, the unit of absorbed dose, Gy stands for Gray. In EM biological interactions, the SAR equations are derived and the characteristics of EM field energy absorption in terms of the SAR are discussed and described on the mathematical basis.

• Korean Chemical Engineering Research
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• 제59권2호
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• pp.239-246
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• 2021

태양열 SiC 입자 유동층 흡열기(내경 50 mm, 높이 150 mm)에서 수력학적 특성 및 기체 열흡수 특성이 연구되었다. 측정 구간 내에서, 기체 속도가 증가할수록 유동층 내 고체체류량은 일정하였으나, 유사한 기체속도 구간(Ug = 0.03-0.05 m/s)에서 미세한 SiC 입자(SiC II; dp=52 ㎛, ρs=2992 kg/㎥)는 굵은 SiC 입자(SiC I; dp=123 ㎛, ρs=3015 kg/㎥) 대비 유동층 내 압력요동의 상대 표준편차는 낮았으며, 프리보드 내 고체체류량은 상대적으로 높은 값을 나타내었다. 미세한 SiC II 입자는 굵은 SiC I 입자 대비 일사량의 변화에 관계없이 상대적으로 높은 일사량 당 흡열기 입출구 온도차를 보였고, 이는 상대적으로 균일한 유동층 내 입자 거동에 의한 층 표면 수용 열의 효율적인 열확산 효과에 더하여, 프리보드 영역에서 비산된 입자에 의한 추가적인 태양열 흡수 및 기체로의 열전달 효과에 기인한다. 본 시스템에서 기체속도 및 유동화 수가 증가할수록 열 흡수 속도 및 열효율은 증가하였다. SiC II 입자는 최대 17.8 W의 열 흡수 속도와 14.8%의 열효율을 보였고, 이는 SiC I 입자 대비 약 33% 높은 값을 나타내었다.

• 대한금속재료학회지
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• 제47권12호
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• pp.866-872
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• 2009

The effects of magnetic powder thickness on electromagnetic wave absorption characteristics in Fe-6.5Si-0.9Cr (wt%) alloy flakes/polymer composite sheets available for quasi-microwave band have been investigated. The atomized FeSiCr powders were milled by using attritor for 12, 24, and 36 h, powder thickness changed from $40{\mu}m$ to $3{\mu}m$ upon 36 h milling. The composite sheet, including thinned magnetic flakes, exhibited higher power loss in the GHz frequency range as compared with the sheets having thick flakes. Moreover, both the complex permeability and the loss factor increased with the decrease in thickness of the alloy flakes. Therefore, the enhanced power loss property of the sheets containing thin alloy flakes was attributed to the flakes of high complex permeability, especially their imaginary part. Additionally, the complex permittivity was also increased with the reduction of flake thickness, and this behavior was considered to be helpful for improvement of the electromagnetic wave absorption characteristics in the composite sheets, including thin alloy flakes.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.493-493
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• 2014

The manufacturing cost of thin-film photovoltics can potentially be lowered by minimizing the amount of a semiconductor material used to fabricate devices. Thin-film solar cells are typically only a few micrometers thick, whereas crystalline silicon (c-Si) wafer solar cells are $180{\sim}300\mu}m$ thick. As such, thin-film layers do not fully absorb incident light and their energy conversion efficiency is lower compared with that of c-Si wafer solar cells. Therefore, effective light trapping is required to realize commercially viable thin-film cells, particularly for indirect-band-gap semiconductors such as c-Si. An emerging method for light trapping in thin film solar cells is the use of metallic nanostructures that support surface plasmons. Plasmon-enhanced light absorption is shown to increase the cell photocurrent in many types of solar cells, specifically, in c-Si thin-film solar cells and in poly-Si thin film solar cell. By proper engineering of these structures, light can be concentrated and coupled into a thin semiconductor layer to increase light absorption. In many cases, silver (Ag) nanoparticles (NP) are formed either on the front surface or on the rear surface on the cells. In case of poly-Si thin film solar cells, Ag NPs are formed on the rear surface of the cells due to longer wavelengths are not perfectly absorbed in the active layer on the first path. In our cells, shorter wavelengths typically 300~500 nm are also not effectively absorbed. For this reason, a new concept of plasmonic nanostructure which is NPs formed both the front - and the rear - surface is worth testing. In this simulation Al NPs were located onto glass because Al has much lower parasitic absorption than other metal NPs. In case of Ag NP, it features parasitic absorption in the optical frequency range. On the other hand, Al NP, which is non-resonant metal NP, is characterized with a higher density of conduction electrons, resulting in highly negative dielectric permittivity. It makes them more suitable for the forward scattering configuration. In addition to this, Ag NP is located on the rear surface of the cell. Ag NPs showed good performance enhancement when they are located on the rear surface of our cells. In this simulation, Al NPs are located on glass and Ag NP is located on the rear Si surface. The structure for the simulation is shown in figure 1. Figure 2 shows FDTD-simulated absorption graphs of the proposed and reference structures. In the simulation, the front of the cell has Al NPs with 70 nm radius and 12.5% coverage; and the rear of the cell has Ag NPs with 157 nm in radius and 41.5% coverage. Such a structure shows better light absorption in 300~550 nm than that of the reference cell without any NPs and the structure with Ag NP on rear only. Therefore, it can be expected that enhanced light absorption of the structure with Al NP on front at 300~550 nm can contribute to the photocurrent enhancement.

• 한국전기전자재료학회논문지
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• 제13권9호
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• pp.758-763
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• 2000

Dielectric strength of insulators made of epoxy composites rapidly decreases due to ageing to interfaces between the matric resin and filler particles. The adhesion variation of interfaces caused by moisture absorption also alters electrical properties that are the basic characteristics of insulators, particularly, in outdoor use. In this paper, electrical properties of epox/SiO$_2$composites were investigated at boiling absorption condition to observe the influences of moisture. In order to analyze the basic physical properties of samples, scanning electron microscopy and DC, AC and impulse voltage dielectric strength were measured. Also, the breakdown time of samples was measured under AC 6[kV] applied voltage, and the variation of lifetime was verified by using Weibull distribution function.

• 한국광학회지
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• 제6권4호
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• pp.259-265
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• 1995

국내 민수용으로 유통되고 있는 20여종의 무반사 안경렌즈들을 선정하여 광학적 특성을 분석하였다. 분광광도계를 사용하여 측정한 반사특성과 투과특성을 렌즈의 굴절력, 각 무반사층들 및 렌즈기층에 의한 영향과 연결시켜 분석하였다. 흡수단 근방에서의 겉보기 흡수스펙트럼은 기층물질에 따라 결정되며 400-700nm의 파장대역에서 대부분의 시료들의 겉보기 흡수스펙트럼과 반사스펙트럼은 강한 양의 상관관계를 보여준다. 예외적으로 기층에 의한 흡수가 큰 렌즈들은 상관관계가 약해지며 이와 같은 기층에 의한 흡수는 무반사 특성에 부정적인 효과를 가진다. 또한 국내에서 제작되는 $SiO_2/TiO_2/SiO_2/ZrO_2/Cr$ 다층박막층을 c-Si 기층위에 성장시키면서 각 단계별로 ex-situ 분광타원해석법으로 분석하여 $TiO_2$ 박막과 $ZrO_2$ 박막의 조밀도가 80% 정도에 불과하며 박막이 두꺼원 짐에 따라 박막에 수직한 방향으로 균일하지 않음을 확인하였다. 마지막으로 실시간, in-suti 측정을 바탕으로하여 엄밀한 사양이 요구되는 다층박막, 초격자박막 등을 재현성있게 성장시킬 수 있는 가능성에 대해 토의하였다.

• 한국세라믹학회지
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• 제33권12호
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• pp.1353-1364
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• 1996

Recently semiconductor doped glasses have attracted attention as nonlinear optical materials because of their large third order nonlinear optical properties. The transparent and homogeneous CdS-doped SiO2 glass thin films were obtained by the dip=coating process of the sol-gel method. Thin films were consisted of glasses containing CdS microcrystallites which were formed by dissolved Cd2+ and S2- ions in a SiO2 matrix solutions. A subsequent thermal treatment of this samples led the formation of colloidal agglomerates and finally of microcrystallites. The size of CdS microcrystallites was about 4 to 15 nm after thermal treatments at various heating conditions. From the optical absorption spectra of the CdS-doped SiO2 glass films it was found that the absorption edge was blue-shifted compared with that of the bulk CdS crystal(~2, 4 eV) and that the amount of energy shift was inversely proportional to the crystal size. And the band gap energy increased with the decrease in crystallite size indicating that the quantum size effects occured.

• 한국진공학회지
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• 제7권3호
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• pp.167-272
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• 1998

ECR plasma CVD를 이용한 SiOF박막은 낮은 유전상수를 가지고 있으며, 기존의 공정과의 정합성이 우수해 다층배선 공정에 채용이 유망한 재료이지만 수분의 흡수로 인한 유전율의 상승과 후속공정의 안정성이 문제점으로 부각되고 있다. 따라서 본 연구에서는 SiOF박막의 내흡습성과 후속공정에서의 안정성을 향상시키기 위하여 SiOF박막을 증착한 후 후속 산소 플라즈마 처리를 행하였다. SiOF박막은 산소 플라즈마 처리를 수행함으로써 SiOF박막의 밀도가 증가하고, 수분과의 친화력이 강한 Si-F 결합이 감소하는 것이 주요한 원인으로 사료된다. 하지만 플라즈마 처리 시간이 5분 이상으로 증가하면 유전율의 증가가 일어난다. 따라서 본 실험에서는 산소 플라즈마 처리조건이 마이크로파 전력이 700W, 공정 압력이 3mTorr, 기판온도가 $300^{\circ}C$일 경우 플라즈마 처리시간은 3분이 적당한 것으로 생각 된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.332-334
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• 1988

Influence of incoherent lamp heating sources on the absorption effect and variation of OSF' size were investigated. The absorption effect on I.R lamp caused by free carrier excitation is greater than that of Tungsten-Halogen lamp. The variation of DSF' size weakly affected by oxidation time.

• Current Photovoltaic Research
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• 제8권3호
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• pp.94-101
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• 2020

This study was trying to focus on achieving high efficiency of multi junction solar cell with thin film silicon solar cells. The proposed thin film Si-Ge/c-Si tandem junction solar cell concept with a combination of low-cost thin-film silicon solar cell technology and high-efficiency c-Si cells in a monolithically stacked configuration. The tandem junction solar cells using amorphous silicon germanium (a-SiGe:H) as an absorption layer of upper sub-cell were simulated through ASA (Advanced Semiconductor Analysis) simulator for acquiring the optimum structure. Graded Ge composition - effect of E_g profiling and inserted buffer layer between absorption layer and doped layer showed the improved current density (J_sc) and conversion efficiency (η). 13.11% conversion efficiency of the tandem junction solar cell was observed, which is a result of showing the possibility of thin film Si-Ge/c-Si tandem junction solar cell.