• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.387-387
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• 2012

결정 Si 및 비정질 Si 태양전지는 환경친화적이며 안정적인 물질로 전력변환 및 에너지 저장 장치에 중요하기 때문에 연구가 활발하게 진행되고 있다. 고효율 Si 태양전지를 제작하여 상용화하기에는 여러 가지 문제점이 있다. 공기와 비교하여 높은 굴절률을 갖고 있기 때문에 발생하는 반사를 줄이기 위해서 필요한 무반사 코팅층(Anti-reflective coating; ARC)은 주로 SiO2 와 SiNx 와 같은 유전체를 이용하여 사용하지만 이들 ARC 증착은 PECVD와 같은 진공장비를 사용하므로 제작 비용이 높아지는 단점이 있다. 나노선 또는 나노 팁과 같은 sub-wavelength 구조를 표면에 만들어 반사율을 줄이는 작업을 통해 ARC 공정비용을 감소하고 효율을 증진하는 연구가 활발히 진행되고 있다. CdS 양자점을 태양전지 표면에 형성함으로 ARC로 해결할 수 없는 단파장영역에 해당하는 부분을 줄이는 연구가 진행되었으며, 비정질의 경우 원기둥 형태의 태양전지 형태와 더불어 지름 방향으로의 PN 접합 나노로드 배열을 만들어 흡수면을 증가하여 효율을 증가한 연구도 진행되었다. 태양전지 표면의 형태를 V-groove 형태로 형성하여 입사하는 태양전지의 광밀도를 증가하는 이론적 결과도 발표되었다. 본 연구에서는 Si 태양전지의 표면변형에 따른 태양전지의 전력변환효율의 변화를 관찰하기 위하여 태양전지 표면의 texture 지름을 $3{\sim}15{\mu}m$, 간격을 $5{\sim}20{\mu}m$로 변화하고, 태양전지 표면의 나노 패턴을 2~10 nm 로 변화하여 반사율과 전력변환효율을 비교하였다. 나노와 마이크로 패턴은 각각 polystyrene nanosphere 와 photo mask를 이용하여 제작하였으며 PN junction Si 태양전지는 spin on dopant 방식으로 제작하여 성능을 조사하였다.

• Korean Journal of Plant Resources
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• v.19 no.1
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• pp.120-125
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• 2006

This experiment was conducted to investigate growth and flowering characteristics of Celosia argentea native to Korea treated by monthly sowing from January 20 to August 20 in the field. As sowing date delayed from January to June, the days to flowering were increased. Seedlings sown on February and March planted in the field on April and May were shorter, 31 days to flower, shorter plant height, much more number of flower than those of sown on May and June planted in the field on July and August which means Celosia argentea may be facultative short day plant. And the seedlings sown on February and March were precious ornamentals for bed plant from summer to fall, however, the seedlings sown on April and May were valued for bed or cut plant producing in fall.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.140-140
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• 2016

유기전계발광소자 (Organic Light Emitting Diode : OLED)는 보조광원이 필요 없고 천연색 표현이 가능하며, 낮은 소비 전력 및 저전압 구동 등의 장점으로 이상적인 디스플레이 구현이 가능하여 차세대 디스플레이로써 많은 이목을 끌고 있으나 제한된 수명과 안정성의 문제점을 안고 있다. 따라서 OLED의 열화 원인을 분석하고 수명을 연장하기 위한 체계적인 방법과 기술 개발이 중요하다. Impedance Spectroscopy는 이온, 반도체, 절연체 등의 벌크 또는 계면 영역의 전하 이동을 조사하는데 사용될 수 있어, OLED에서도 Impedance Spectroscopy를 이용하여 전하수송과 전자주입 메커니즘 등 폭넓은 전기적 정보를 얻을 수 있다. 본 연구에서는 Impedance Spectroscopy를 이용하여 경과시간에 따른 OLED의 임피던스 특성을 측정하여 열화 메커니즘을 분석하였다. 본 연구에서 OLED는 ITO / 2-TNATA (4,4,4-tris2-naphthylphenyl-aminotriphenylamine) / NPB (N,N'-bis-(1-naphyl)-N, N'-diphenyl-1,1'- biphenyl-4,4'-diamine) / Alq3 (tris(quinolin-8-olato) aluminum) / Liq / Al으로 구성된 녹색 형광 OLED를 제작하였다. OLED의 전계 발광 특성을 측정하기 위한 전원 인가장치로 Keithley 2400을 사용하여 전압과 전류를 인가하였고, 소자에서 발광된 휘도 및 발광 스펙트럼은 Photo Research사의 PR-650 Spectrascan을 사용하여 암실 환경에서 측정하였다. 임피던스 스펙트럼은 컴퓨터 제어 프로그래밍이 가능한 KEYSIGHT사의 E4990A를 사용하여 측정하였다. 임피던스 측정 전압은 0 V부터 2 V 간격으로 8 V까지, 주파수는 20 Hz에서 2 kHz의 범위로 설정하여 측정하였다. I-V-L과 임피던스 특성은 24 시간의 간격을 두고 실온에서 측정하였다. 그림은 경과시간에 따른 녹색 형광 OLED의 인가전압 2 V, 6 V의 Cole-Cole plot을 나타낸 것이다. 문턱전압 미만인 인가전압 2 V에서는 소자를 통하여 전류가 흐르지 않아 큰 반원 형태를 나타내었고, 시간이 경과함에 따라 소자 제작 직후엔 실수 임피던스의 최댓값이 $8982.6{\Omega}$에서 480 시간 경과 후엔 $9840{\Omega}$으로 약간 증가하였다. 문턱전압 이상인 인가전압 6 V에서는 소자 제작 직후 실수 임피던스의 최댓값이 $108.2{\Omega}$으로 작은 반원 형태를 나타내나 시간이 경과함에 따라 방사형으로 증가하는 것을 확인 할 수 있었고, 672 시간 경과 후엔 실수 임피던스의 최댓값이 $9126.9{\Omega}$으로 문턱 전압 미만 일 때와 유사한 결과를 나타내었다. 이러한 임피던스의 증가 현상은 시간이 경과함에 따라 OLED의 열화에 의한 것으로 판단된다.

• Korean Journal of Plant Resources
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• v.26 no.1
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• pp.68-74
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• 2013

This study was conducted to analyse the effectiveness of shading on growth and arsenic absorption of Pteris multifida, known as hyperaccumulator of arsenic, from paddy soils contaminated with heavy metals. Study was carried out in paddy soil polluted by arsenic near the former Janghang smelter. P. multifuda in the same growth stage was planted with $20{\times}20cm$ intervals in each experimental plot ($2{\times}2m$), and cultivated for 24 weeks. The growth of P. multifuda according to shading conditions was evaluated, the accumulated amount of arsenic in plants and arsenic variation in the soil was analyzed using ICP. In the result of this study, the growth of P. multifida cultivated under shading treatment was vigorous than non-shading. Accumulated amount of arsenic in aerial parts of P. multifida cultivated under non-shading ($169.8mg{\cdot}kg^{-1}$) was slightly higher than shading ($140.9mg{\cdot}kg^{-1}$), and those in underground part were almost the same. But the growth was great in 70% shading treatment. Therefore, arsenic contents absorbed from soils was much higher in shading treatment. Arsenic translocation rate (TR) of P. multifida was very high (0.87~0.89) regardless of shading conditions. So arsenic in soil could be efficiently eliminated by removal of aerial parts.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.10a
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• pp.40-40
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• 2018

비고사리과(Lindsaeaceae) 버들일엽[Laxqgramme saliciblia (Makino) Makino]은 잎이 녹색의 단엽으로 버들처럼 보여 관상가치가 높아 조경소재로 이용되는 착생식물이다. 또한 식물구계학적 특정식물종 V급, 적색자료집 VU급, 국외반출 승인대상종에 수록된 식물로 생태학적 보전이 요구되며, 개체수도 적은 편으로 알려져 있다. 본 연구는 보전이 요구되는 버들일엽의 전엽체 증식 및 포자체 형성을 위한 기내 외 번식조건을 구명하고자 수행되었다. 서귀포시 상효동 일대에서 식물을 획득하였으며, 기내에서 포자를 발아시켜 획득한 전엽체를 8주 간격으로 계대배양하면서 실험재료를 확보하였다. 전엽체 증식에 적합한 배양배지를 선발하고자, 전엽체 300mg을 다진 후 배지종류와 농도를 달리한 배지(Knop, 1/4, 1/2 및 1MS)에 8주간 배양하였다. 배양실은 온도 $25{\pm}1.0^{\circ}C$, 광도 $30{\pm}1.0{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$(16/8h)로 조절되었다. 연구의 결과, 1/2MS배지에서 전엽체의 생체중이 5.8g으로 가장 많이 증가하였으며, 형태형성의 발달도 주걱형의 전엽체로 정상적으로 발달하였다. 기외 포자체 형성에 적합한 토양조건을 확인하고자, 인공토양(원예상토, 피트모스, 펄라이트 및 마사토)의 비율을 달리하여 5종류의 혼합토양을 조성하였다. 준비된 토양을 사각분($7.5{\times}7.5{\times}7.5cm$)에 충진하고, 전엽체 1g을 10초간 분쇄한 다음 토양표면에 분주하여 16주간 재배하였다. 재배환경은 온도 $25{\pm}1.0^{\circ}C$, 광도 $43{\pm}2.0{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$(16/8h) 및 습도 $72{\pm}2.0%$로 조절되었다. 연구의 결과, 원예상토가 많은 비율로 혼합된 처리에서 포자체의 형성이 확인되었다. 원예상토와 펄라이트를 2:1(v:v)로 혼용한 토양, 원예상토와 마사토를 2:1(v:v)로 혼용한 토양, 원예상토 단용한 토양에서 각 28.5, 23.0, 22.3개로 조사되었다.

• Solar Energy
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• v.17 no.4
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• pp.3-11
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• 1997

Because grain boundaries in polycrystalline silicon act as potential barriers and recombination centers for the photo-generated charge carriers, these defects degrade conversion effiency of solar cell. To reduce these effects of grain boundaries, we investigated various influencing factors such as thermal treatment, various grid pattern, selective wet etching for grain boundaries, buried contact metallization along grain boundaries, grid on metallic thin film. Pretreatment above $900^{\circ}C$ in $N_2$ atmosphere, gettering by $POCl_3$ and Al treatment for back surface field contributed to obtain a high quality poly-Si. To prevent carrier losses at the grain boundaries, we carried out surface treatment using Schimmel etchant. This etchant delineated grain boundaries of $10{\mu}m$ depth as well as surface texturing effect. A metal AI diffusion into grain boundaries on rear side reduced back surface recombination effects at grain boundaries. A combination of fine grid with finger spacing of 0.4mm and buried electrode along grain boundaries improved short circuit current density of solar cell. A ultra-thin Chromium layer of 20nm with transmittance of 80% reduced series resistance. This paper focused on the grain boundary effect for terrestrial applications of solar cells with low cost, large area, and high efficiency.

• The Korean Journal of Malacology
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• v.29 no.4
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• pp.263-272
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• 2013

The development of swift's scallop Chlamys swiftii, reared in the laboratory, has been examined through the investigation of morphological characteristics in fertilized egg, larvae and juvenile. Eggs were fertilized with a dilute sperm solution to improve the survival of fertilized eggs. Developing larvae were maintained at a temperature of $16{\pm}0.5^{\circ}C$ and salinity concentration of 33 ppt. We have investigated the fertilization rates and egg number spawned at several stimulating conditions such as sunlight exposure, air dry, seawater temperature rise ($5^{\circ}C$) and seawater temperature rise ($5^{\circ}C$) after exposure of air dry for spawning induction of swift's scallop Chamys swiftii. Stimulation treated with sunlight exposure and seawater temperature rise ($5^{\circ}C$) have shown the spawning number of 700,000-900,000 and 700,000-800,000 per individual, respectively while stimulation treated with seawater temperature rise ($5^{\circ}C$) after exposure of air dry have shown the high spawning number of 1,000,000-1,500,000 per individual. Survival rate of D-shaped larvae of swift's scallop put into the different seawater temperatures of $8^{\circ}C$, $12^{\circ}C$, $16^{\circ}C$, $20^{\circ}C$ and $24^{\circ}C$ has been 4.1%, 11.6%, 32.7%, 18.6% and 3.2%, respectively. Fertilized eggs with the diameter of $72{\mu}m$ developed into trochophore larvae of $103{\pm}3.8{\mu}m$ shortly after 35 hours and to D larvae of $129{\pm}10.4{\mu}m$ shell length within 72 hours. It took 336 hours to become initial Umbo-stage larva of $145{\pm}16.8{\mu}m$ shell length. Post larvae, which have been $197{\pm}13.6{\mu}m$ shell length, spontaneously have settled in the attachment substances. It have required 528 hours from fertilized eggs to early attached juvenile to become initial juvenile size of $245{\pm}15.8{\mu}m$ shell length.

• The Korean Journal of Mycology
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• v.9 no.4
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• pp.169-176
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• 1981

Survey of sesame crop in the cultivators' field in the district of Daejeon, Yuseong, Sintanjin, Nonsan and Keumsan revealed that Alternaria and Corynespora blights of sesame were wide spread and caused severe damage to sesame plants. Symptoms of a new disease of sesame in Korea caused by Alternaria sesami were spreading, dark-brown to black, water-soaked lesions which often could be traced the entire length of the stem. In severe infections, several lesions coalesced together involving a major portion of the blade and the infected leaves dried and usually dropped off. Symptoms of Corynespora blight, caused by Corynespora cassiicola, were irregular shaped, concentrically-zoned, light brown to reddish brown lesions which later coalesced and caused defoliation. Stem lesions were long, reddish brown streaks that often coalesced, blighting the plants. The optimum temperatures for mycelial growth of A. sesami and C. cassiicola were about $27^{\circ}C$ and sporulations of these 2 fungi were stimulated under alternating light and darkness. Mycelial growth and sporulation of A. sesami and C. cassiicola were the greatest on sesame oatmeal agar (SOA) and potato dextrose agar (PDA), respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.1
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• pp.101-112
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• 2015

II~VI compound semiconductors, $Zn_xCd_{1-x}S$ thin films have been synthesized onto indium-tin-oxide(ITO) coated glass substrates using thermal evaporation technique. The composition ratio x($0{\leq}x{\leq}1$) was varied to fabricate different kinds of $Zn_xCd_{1-x}S$ thin films including CdS(x=0) and ZnS(x=1) thin films. Then, the deposited thin films were thermally annealed at $400^{\circ}C$ to enhance their crystallinity. The chemical composition and electronic structure of films were investigated by using X-ray photoelectron spectroscopy(XPS). The optical energy gaps of the samples were determined by ultra violet-visible-near infrared(UV-Vis-NIR) spectroscopy and were found to vary in the range of 2.44 to 3.98 eV when x changes from 0 to 1. Finally, we measured the THz characteristics of the $Zn_xCd_{1-x}S$ thin films using THz-TDS(time domain spectroscopy) system to identify the capability for electronic and optical devices in THz region.

• Korean Journal of Agricultural Science
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• v.40 no.2
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• pp.107-113
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• 2013

We tested fruits quality and skin coloration of two pear cultivar 'Wonhwang' and 'Whasan' produced by bagging with different kinds of paper bags in the Cheonan area, Chungnam Province, Korea. The fruits were bagged at 35, 45, 55 or 65 days after full bloom (DAFB) with 3 kinds of double layer paper bag which consisted of grey color, yellow color and newspaper for outer layer. The great extent of light interruption was observed in grey colored outer paperbag among three kinds of paperbag which showed only 0.46% of lowest light transmittance when compared with 43.7% and 40.0% of yellow paper and newspaper, respectively. The development of skin redness ($a^*$) increased with the delay of bagging time in two pear cultivars. But the fruits treated at 65 DAFB showed uneven coloration and excessive development of redness which represented low fruit external appearance value. Uniform flesh firmness was attained at the fruits bagged with grey outer color paperbag regardless of bagging time, although the fruit quality indices including soluble solids and titratable acidity did not change significantly by using different kind of fruit bags and bagging time in two pear cultivar. Based on our results, it was explained that the grey-colored fruit bag had positive effect on the development of skin coloration without any detrimental effect on fruit quality factors in 'Wonhwang' and 'Whasan' pears.