• Solar Energy
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• v.5 no.2
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• pp.46-53
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• 1985

Hydrogenated amorphous silicon solar cells which are fabricated by photo-chemical vapor deposition (photo-CVD) system has been investigated. In the photo-CVD system which consists of three separate reaction chambers, low-pressure mercury lamp has been used as a light source. The main reactant ($Si_2H_6/He$) gases which are premixed with a small amount of mercury vapor in a mercury-vaporizer kept at $50^{\circ}C$ have been used. Using $C_2H_2$ and $SiH_2(CH_3)_2$ as the carbon source, p-type wide band gap a-SiC:H films have been obtained. The result has been found that the undoped layers of the pin/substrate solar cells are influenced by the residual impurities, such as phosphorus and boron during the deposition process. By minimizing the effect of the impurities in the i-layer and optimizing conditions at the p-layer and p/i interface, the energy conversion efficiency of 9.61 % under AM-1 ($100mW/Cm^2$) has been achieved for pin/substrate solar cells illuminated through their p-layers, using the three separate reaction chamber apparatus. It is expected that a-SiC:H solar cells with the energy conversion efficiency over 10% have been fabricated by Photo-CVD method.

• Journal of Environmental Science International
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• v.5 no.1
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• pp.61-69
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• 1996

The combined wastewater of municipal landfill leachate and municipal sewage was treated using several sets of bench-scale aerated circulating system including porous media. Investigated items in this experiment were the dominant protozoa and metazoa in this system, the variation of microfauna relationship between operating condition and dominant genera. Also considered the factors determining dominant genera and their role. The outcome of this research is as follows; 1. Aspidisca, Vorticella, Truhellophyllum, Lecane, Philodina, Cyclops were mainly appeared prior to combinding leachate, while Trachelocerca, Bodo, Glaucoma were the dominant genera after combinding leachate. 2. As to metazoa, Nematode and Philodina were not influenced by 5oA leachate mixing ratio, meanwhile Crustacea has high sensitivity for increased leachate mixing ratio and it was not appeared in 5% leachate mixing ratio. 3. The appropriate treatability could'nt be expected at the above 10% leachate mixing ratio. Especially, in the condition of 20% leachate mixing ratio, all of the microfauna were affected damage seriously on their existence. Meanwhile hydraulic retention time, substrate loading rate and slut자e production rate didn't give notable influence on increasing the number of microfauna. 4. As to protozoa, saprozoic and holozoic species were appeared commonly and polysaprobic species were dominent. 5. Filamentous organsms were nearly not affected by leachate mixing. It seems that they could live without any trouble at the 10% leachate mixing ratio, if the substrate is sufficient. 6. Diversity of microfauna had a reducing trernd as the sewage was mixed with leachate.

• Journal of Sensor Science and Technology
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• v.19 no.6
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• pp.497-503
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• 2010

This paper reports a chemomechanical explosive sensor based on a thin polymer membrane. The sensor consists of thin parylene membrane and electrodes. Parylene membrane is functionalized with 4-mercaptophenol which interacts strongly with nitrotoluene based explosives. The membrane deflection caused by molecular interaction between the surface and explosives is monitored by capacitance between the membrane and the substrate. To measure the capacitance, electrodes are formed on the membrane and the substrate. While the previous cantilever system requires a bulky optical measuring system, this purely electric monitoring method offers a compact and effective system. Thus, this explosive sensor can be readily miniaturized and used in the field. The developed sensor can reliably detect dinitrotoluene and its limit of detection is evaluated as approximately 110 ppb.

• Korean Journal of Agricultural Science
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• v.37 no.2
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• pp.199-207
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• 2010

This research was conducted to determine the influence of physiological and chemical properties of root substrates on the growth of the daughter plants of 'Maehyang' strawberry produced by bag culture. The daughter plants produced by stock plants during bag culture were individually separated and grown in 10-cm diameter plastic pots containing six different formulations of root substrates: a) 50% peatmoss plus 50% vermiculite (5:5 by volume, A), b) 70% peatmoss plus 30% perlite (7:3, B), c) 70% coir dust plus 30% perlite (7:3, C), d) mixture of 35% coir dust, 35% peatmoss, and 30% perlite (3.5:3.5:3.0, D), e) mixture of 20% rice hull, 70% coir dust, and 10% perlite (2:7:1, E), and f) 30% rice hull plus 70% coir dust (30:70, F). The container capacity and air filled porosity of the growing medium varied greatly among the six substrate formulations evaluated. The substrates E and F had less container capacity and higher air-holding spaces than the rest of the formulations. Therefore, these two formulations (E and F) may cause a problem in water management during the production of healthy daughter plants. The substrate formulations A, B, and D retained higher nitrogen (N) concentrations than other formulations containing coir dust or rice hull. The substrate formulations E and F which contained rice hull had lower N, phosphorus (P), and potassium(K) concentrations than other substrate formulations containing coir. The quality of the daughter plants grown in all six different substrate formulations was good with the crown diameters at around 10 mm. Fresh weights of the daughter plants grown in substrate formulations A, C, and D were higher than those obtained from B, E, and F. Dry weights of the daughter plants showed a similar trend. The daughter plants having high fresh and dry weights and increased crown diameter are in demand by the industry. For this reason, the substrate formulations A, C and D can readily be used as potting mixes during the production of 'Maehyang' strawberry transplants utilizing the bag culture system.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.185-185
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• 2013

최근 의료 영상 센서는 급속도로 발전을 이룩하여 미세 병변의 위치와 그 크기를 진단하는 데에 많은 이용이 되고 있다. 하지만 기존 flat panel형태의 의료영상 센서는 인체의 굴곡으로 인한 영상 왜곡으로 발전의 한계에 이르고 있는 실정이다. 이 영상 왜곡으로 인한 오진은 환자에게 불필요한 피폭, 수술적 요법, 약물치료 등 환자에게 치명적인 의료사고를 일으킬 수 있다. 이러한 한계를 극복하기 위하여 flexible substrate을 이용한 투명전극들이 의료영상 센서로서의 적용을 연구 되어 졌다. IZO, ITO, FTO 등의 투명전극들 중 Indium Tin Oxide(ITO)는 다른 전극에 비해 높은 투명도와 낮은 저항으로 인하여 다양한 부분에서 널리 이용 되고 있다. 그러나 ITO를 flexible substrate로 적용 시 불충분한 resistivity와 기계적 강도를 지니고 있으며, 유연성을 위해 전극 재료의 두께를 감소시키면 전도성의 문제를 일으키는 단점이 있는 것으로 알려져 있다. 이러한 문제점을 보완 및 해결하기 위하여 본 연구에서는 sputtering magnetron system를 이용하여 polyethylene terephthalate(PET) substrate 위에 ITO을 증착함으로써 전기적 특성을 알아보았다. PET 필름의 크기를 55 절단하였고 증착 온도는 고온에서 수축하는 PET 필름의 물성을 고려하여 $23^{\circ}C$로 설정 하였다. 가스의 분압 비를 Ar는 50ccm으로 고정하고 O2의 비율을 각각 0, 0.2, 0.4, 0.8, 1ccm으로 나눈 후, 비율에 따라 각각 30, 60, 90sec간 sputtering 증착을 하였다. 또한 각각 30, 60, 90sec간 sputtering 증착하여 O2 유량과 sputtering 증착 시간의 변화에 따른 ITO의 전도특성과 유연성에 대한 전도특성을 측정하였다. 유연성을 측정하기 위해선 bending 각도를 각각 $0^{\circ}$ $30^{\circ}$, $45^{\circ}$, $60^{\circ}$로 구부린 후, Two-point probe를 이용하여 변화된 저항을 통해 ITO의 전기적 성질의 변화를 측정 하였다. 측정결과 flexible ITO substrate의 전도특성은 sputtering 증착시간이 증가할수록 저항 값이 낮아지는 것을 확인하였지만, O2 유량이 증가 시 저항이 낮아지다가 다시 증가하는 결과를 알 수 있었다. 본 연구에서는 Ar:O2의 50:0.8의 조건에서 90sec동안 sputtering 증착한 ITO가 131 ${\Omega}/cm^2$의 저항 값이 측정 되었고 다른 조건에서는 164 ${\Omega}/cm^2$에서 4.7 $k{\Omega}/cm^2$까지 저항변화를 가져 Ar:O2의 50:0.8의 조건이 최적화에 좋은 조건이라 판단하였다. 또한 50:0.8의 조건의 ITO의 경우 bending test시에서도 131 ${\Omega}/cm^2$에서 316 ${\Omega}/cm^2$ 정도의 안정적인 저항변화를 가지는 반면 다른 조건에서는 128 ${\Omega}/cm^2$에서 6.63 $k{\Omega}/cm^2$까지의 변화를 나타나 기계적 형상변화에도 분압비가 영향을 주는 것을 확인 할 수 가 있었다. bending 각도에 따른 저항의 변화를 측정하였을 시, 각도 변화에 따라 중심부의 저항 값이 $60^{\circ}$에서 가장 높은 변화가 나타나 전기저항이 높아진 원인을 찾기 위해 Scanning Electron Microscope (SEM)촬영을 한 결과 저항값이 높아짐에 따라 ITO의 압축응력이 작용하는 부근에 Crack이 발생함을 알 수 있었다. 이러한 결과로 flexible ITO substrate의 Crack발생률을 최소화 시키고 bending시 전도성을 유지하기 위해서는 가스의 유량 최적화가 flexible substrate의 기계적형상변화에 대한 ITO의 내구성을 향상시킬 수 있는 해답이 될 것으로 사료된다.

• Journal of Bio-Environment Control
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• v.31 no.4
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• pp.292-299
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• 2022

This study was conducted to analyze physical and chemical properties of horticultural substrates and response of hydroponically grown two cultivars of 'Namcheon' and 'Somirang' perilla by four different substrates: coir (chip:dust = 5:5), perlite, granular rockwool, and commercial mixed substrate (cocopeat:peatmoss:vermiculite:perlite: zeolite = 50:25:10:10:5). There were no significant differences in EC and pH according to substrates. Container capacity was the greatest in granular rockwool, and it showed appropriate levels in mixed substrate and coir. Air space was higher in coir and perlite than the other treatments. Bulky density reached a proper standard in all substrates excepting coir. The leaf length and width of 'Namcheon' indicated the most in mixed substrate, though the value of 'Somirang'was greatest in coir substrate. The leaf weight of both cultivars was highest in mixed substrate, and relatively low in coir and perlite. The total yield of leaves was separated by two groups: higher group, which are mixed substrate and granular rockwool, and lower group, which are coir and perlite. There was a large gap by 28% between these two groups. Therefore, this study suggests that substrates with high water holding capacity such as mixed substrate or granular rockwool are most suitable for the hydroponic cultivation of perilla, which require sufficient moisture supply to the root zone.

• Horticultural Science & Technology
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• v.28 no.6
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• pp.1057-1065
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• 2010

Recent urban concerns over environmental problems have furthered interest in green roof system. Plant growth and load bearing capacity of an underlying roof are key factors to determine an optimal system. This study was carried out to develop an optimal extensive green roof system for shrubs assessing the effects of substrate type and soil depth on the growth of $Rhododendron$ $indicum$ Sweet. in the experimental systems with different soil types and depths from 2001 to 2008. Substrate types of perlite alone and blended with sandy loam (v/v, 1:1) were used on the experimental systems with depths of 30 cm, 45 cm, and 60 cm. The survival rate of the plants on the perlite alone + 45 cm soil depth system (RS-A-45) was 100% during the experimental period, while those on the perlite alone + 30 cm soil depth system (RS-A-30) and perlite blended + 60 cm soil depth system (RS-B-60) showed 33% and 67%, respectively, in 2008. The overall plant growth and soil properties of RS-A-45 were superior to the others. At 8 years after installation, the total weight of RS-A-45 including plant fresh weight was about $376.6kg{\cdot}m^{-2}$ in field capacity indicating RS-A-45 can be optimal extensive and light weight green roof system.

• Korean Journal of Microbiology
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• v.42 no.3
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• pp.195-198
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• 2006

Lethal toxin is a critical virulence factor of anthrax. It is composed two protein: protective antigen (PA) and lethal factor (LF). PA binds to specific cell surface receptors and, forms a membrane channel that mediates entry of LF into the cell. LF is a zinc-dependent metalloprotease, which cleaves MKKs [MAPK (mitogen-activated protein kinase) kinases] at peptide bonds very close to their N-termini. In this study, we suggest application of cell-based assays in the early phase of drug discovery, with a particular focus on the use of yeast cells. We constructed MEK1 expression system in yeast to determine LF activity and approached cell-based assay system to screen inhibitors, in which the results covering the construction of LF-substrate in yeast expression vector, expression, and LF-mediated proteolysis of substrate were described. These results could provided the basic steps in design of cell-based assay system with the high efficiency, rapidly and easy way to screening of inhibitors.

• Journal of the Korean Vacuum Society
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• v.18 no.4
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• pp.296-301
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• 2009

An inductively coupled plasma assisted atomic layer deposition(ICP-ALD) system has been constructed for the deposition of ZnO thin films, and various experiments of ZnO thin films on p-type Si(100) substrates have been carried out to find the self-limiting reaction conditions for the ICP-ALD system under non-plasma circumstances. Diethyl zinc[$Zn(C_2H_5)_2$, DEZn] was used as the zinc precursor, $H_2O$ as the oxidant, and Ar as the carrier and purge gas. At the substrate temperature of $150^{\circ}C$, atomic layer deposition conditions based on self-limiting surface reaction were successfully obtained by series of experiments through the variation of exposure times for DEZn, $H_2O$, and Ar. ZnO deposition was repeated at different substrate temperatures of $90{\sim}210^{\circ}C$. As a result, the thermal process window(ALD window) for ZnO thin films was observed to be $110{\sim}190^{\circ}C$ and the average growth rate was measured to be constant of 0.29 nm/cycle. Properties of the film's microstructure and composition(Zn, O, etc.) were also studied. As the substrate temperature increases, the crystallinity was improved and ZnO(002) peak became dominant. The films deposited at all temperatures were high purity, and the films deposited at high temperatures had the composition ratio between Zn and O closer to one of a stable hexagonal wurtzite structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.220-220
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• 2013

Surface-normal transmission electro-absorption modulator (EAM) are attractive for high-definition (HD) three-dimensional (3D) imaging application due to its features such as small system volume and simple epitaxial structure [1,2]. However, EAM in order to be used for HD 3D imaging system requires uniform modulation performance over large area. To achieve highly uniform modulation performance of EAM at the operating wavelength of 850 nm, it is extremely important to remove the GaAs substrate over large area since GaAs material has high absorption coefficient below 870 nm which corresponds to band-edge energy of GaAs (1.424 eV). In this study, we propose and experimentally demonstrate a transmission EAM in which highly selective backside etching methods which include lapping, dry etching and wet etching is carried out to remove the GaAs substrate for achieving highly uniform modulation performance. First, lapping process on GaAs substrate was carried out for different lapping speeds (5 rpm, 7 rpm, 10 rpm) and the thickness was measured over different areas of surface. For a lapping speed of 5 rpm, a highly uniform surface over a large area ($2{\times}1\;mm^2$) was obtained. Second, optimization of inductive coupled plasma-reactive ion etching (ICP-RIE) was carried out to achieve anisotropy and high etch rate. The dry etching carried out using a gas mixture of SiCl4 and Ar, each having a flow rate of 10 sccm and 40 sccm, respectively with an RF power of 50 W, ICP power of 400 W and chamber pressure of 2 mTorr was the optimum etching condition. Last, the rest of GaAs substrate was successfully removed by highly selective backside wet etching with pH adjusted solution of citric acid and hydrogen peroxide. Citric acid/hydrogen peroxide etching solution having a volume ratio of 5:1 was the best etching condition which provides not only high selectivity of 235:1 between GaAs and AlAs but also good etching profile [3]. The fabricated transmission EAM array have an amplitude modulation of more than 50% at the bias voltage of -9 V and maintains high uniformity of >90% over large area ($2{\times}1\;mm^2$). These results show that the fabricated transmission EAM with substrate removed is an excellent candidate to be used as an optical shutter for HD 3D imaging application.