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Salting Up of Chemically Modified Graphene to Assemble Large-Scale Transparent Conductive Films
Lee, Kyueui,Lee, Haeshin,Ryu, Seongwoo American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.11
<P>I report a method for assembling large-scale transparent conductive films (TCFs) through the phenomenon of 'salting up' of chemically modified graphene (CMG) in the presence of metallic salts. The method described herein was inspired by the well-known protein purification process, 'salting-out.' In contrast, addition of hydrophobic CMGs to the solution of a salt results in 'salting-up' of CMGs. Owing to the presence of the salt, dehydrated CMG flakes spontaneously form an extremely thin layer at the air-water interface. The salted-up CMGs spontaneously form an extremely thin layer of CMGs at air-water interface, which is a useful method to prepare a conducting film with an extremely largearea. This CMG film can be transferred to any other flexible substrate as a TCF film and be enlarged to a greater scale depending on size of air-water interface. I demonstrate a new way to fabricate TCF film that can be applied in the fabrication of large scale graphene-based electronic devices.</P>
Lee, Sunghoon,Jeon, Byungjoo,Kang, Taewook,Lee, Wunho,Malik, Afandi Mohammad,Park, Seongwoo,Lim, Jimin,Park, Boowon,Jeong, Yongseok,kim, Jongsu Elsevier 2018 Journal of luminescence Vol.196 No.-
<P><B>Abstract</B></P> <P>Green-emission Zn<SUB>2</SUB>SiO<SUB>4</SUB>:Mn<SUP>2+</SUP> powder phosphor was applied for powder electroluminescence device through a screen printing method. The EL device consisted of silver nanowires as top electrode, 6μm-thick Zn<SUB>2</SUB>SiO<SUB>4</SUB>:Mn<SUP>2+</SUP> phosphor layer, 45µm -thick BaTiO<SUB>3</SUB> dielectric layer, and metal bottom electrode. The EL device showed the strong 525nm green emission spectrum. Its luminance-voltage dependence showed the exponential increase, and its luminance-frequency dependence showed the linear increase and then saturation behavior. It is notable that its temperature dependence showed the constant behavior at lower temperature, and then the drastic rising pattern up to Curie temperature of the dielectric layer (~ 120°C), and then the thermal quenching trend. The maximum luminance was 0.96cd/m<SUP>2</SUP> where the power consumption was 250W/m<SUP>2</SUP> at 420Vp and 400Hz, and thus the luminous efficiency was 0.012lm/W.</P>
The Effects of Spatial Factors on the Incidence of Violent Crime in Korea, 2005-2015
Lee, Kyungjae,Choi, Eunji,Lee, Seongwoo Asian Society for Innovation and Policy 2021 Asian Journal of Innovation and Policy Vol.10 No.2
While many criminal studies have focused on the motivation of offenders and avoidance of victimization in the micro perspective, there have been a number of theoretical developments emphasizing space as a direct factor that influences the incidence of crime. The main purpose of this study is to analyze the effects of regional characteristics and violent crime incidence in Korea. Applying diverse spatial econometrics models that have less been utilized in the crime literature, this study finds an important association between spatial accessibility and crime incidence. The results suggest that the type of predominant business and the level of road accessibility affect the vulnerability of areas with respect to the incidence of violent crime. This study concludes with some important implications for urban planners and policymakers with respect to crime control and prevention.
Seongwoo Choi,Juhee Lee,Yeomyeong Lee,Pil Joo Kim,Ju-Sik Cho,Yong Hwa Cheong,Yo-Sup Rim,Sang Yoon Kim 한국토양비료학회 2020 한국토양비료학회지 Vol.53 No.4
Ethephon is one of the chemical stimulator of crop growth that is also considered as a structural analogue of coenzyme M (CoM), having a promising potential for methanogenic inhibitor. However, the effect of ethephon application on greenhouse gas (GHG) emissions under rice cultivation has not been studied yet. In this pot experiment, different levels of ethephon (0, 2.5, 5 and 10 ㎎ L<SUP>-1</SUP>) were applied at the presence or absence of manure compost as an organic amendment to study its effect on GHGs emissions in particular CH₄ and rice productivity during the cultivation. Application of ethephon effectively suppressed CH₄ emissions in particular the initial periods (ca. 3 weeks) right after the application as compared with control soil during rice cultivation, but did not significantly affect N₂O emissions. In addition, the maximum CH₄ reduction (82% reduction over control) was found at 10 ㎎ L<SUP>-1</SUP> ethephon application right after its addition for 3 weeks during rice cultivation. Rice productivity and yield properties were mainly affected by ethephon application, enhancing ripened grains and number of grains per panicle. Soil properties were not influenced by ethephon application except for available phosphate, which is probably due to enhanced root growth in rhizosphere soils. Conclusively, ethephon could be a new and pioneering amendment for reducing CH₄ emission in particular at the initial 3 weeks after the application without increasing other GHG emissions and enhancing rice productivity in paddy soils.
Yeomyeong Lee(이여명),Hyerin An(안혜린),Juhee Lee(이주희),Seongwoo Choi(최성우),Sang Yoon Kim(김상윤) 한국토양비료학회 2021 한국토양비료학회 학술발표회 초록집 Vol.2021 No.11
Nitrogen (N) fertilization improves crop yield, but may cause serious environmental problems, increasing ammonia (NH₃) and greenhouse gases (GHGs including CO₂, CH₄ and N₂O) emissions, requiring rational fertilization strategy for a better agroecosystem. Organic fertilizer can improve soil cation exchangeable capacity, which could decrease potential N losses and increase crop yield. However, combined application of organic and inorganic fertilizers was not systematically investigated. Our study investigated NH₃ volatilization, GHGs emissions, their intensity (GHGI), soil properties, and productivity during maize and cabbage cultivation period (two cropping seasons in a year) in upland field. The different treatments were installed with equivalent N rate including NPK (sole inorganic fertilizer as urea), compost (sole compost), NPK+compost (inorganic fertilizer and compost, 50%:50%) except control (no fertilizer). During two cropping periods, total cumulative NH₃ volatilizations were significantly increased with all fertilizations as compared to the control. Compost, NPK+compost applications were effective on mitigating NH₃ emissions during cultivation although the same rate of N was incorporated in all treatment except the control. As compared to NPK treatment, compost (0.83 g m<SUP>-2</SUP>), NPK+compost (0.92 g m<SUP>-2</SUP>) applications effectively mitigated N₂O emissions by ca. 54-59% as compared to NPK treatment (2.0 g m<SUP>-2</SUP>). CO₂ and CH₄ emissions were increased with fertilizations, but there was not significant difference among those treatments. Maize and cabbage productivities significantly increased with N fertilizations, but was highest at NPK which did show significant difference with NPK+compost, improving overall soil quality including soil pH, soil organic matter content, available phosphorus, and CEC etc. The GHGI, a sustainable index, was lowest in NPK+compost treatment (2.54 Mg Mg<SUP>-1</SUP>) followed by control (3.36 Mg Mg<SUP>-1</SUP>) > NPK (3.30 Mg Mg<SUP>-1</SUP>) ≒ compost (3.30 Mg Mg<SUP>-1</SUP>), suggesting the promising N management practice in upland soils. Conclusively, combined amendments of inorganic and organic fertilizers could be a sustainable and promising way to mitigate N losses, greenhouse gas emissions, and to enhance crop productivity and soil quality in maize and cabbage cultivated soils.