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Sand Dam Development Directions of Mid-mountain Area for Source Water against Drought
( Donghwan Oh ),( Chihyung Lee ),( Dongyoung Koo ),( Sohee Yang ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2
The demand has been increased rapidly about measures regarding the drought in the mid-mountain area, where is a blind area for a water supply because of the continuous drought. However, to date, there is not yet sufficient research for the fundamental solution. A sand dam is a type of underground dam which is installed dam or weir in valley or stream, and secured space is filled with pervious materials such as sand and then store water in that pore. This is can be applied in Korea where is difficult to construct due to stream environment and ecosystem preservation. This study is to analyse the case of designing a sand dam at domestic and foreign and develop the optimised system for water supply and secure source water in the mid-mountain area in domestic where frequent drought damage. The investigate suggests the development directions of the sand dam in the mid-mountain area connected with the existing water installations and erosion control dam which are based on the case of construction in the mid-mountain area connecting with foreign development cases with the erosion control dam and water intake facilities.
Oh, Hwan Hee,Ko, Young-Gwang,Uyama, Hiroshi,Park, Won Ho,Cho, Donghwan,Kwon, Oh Hyeong Hindawi Publishing Corporation 2014 BioMed research international Vol.2014 No.-
<P>Rapid cell growth and rapid recovery of intact cultured cells are an invaluable technique to maintain the biological functions and viability of cells. To achieve this goal, thermoresponsive polystyrene (PS) nanofibrous mat was fabricated by electrospinning of PS solution, followed by the graft polymerization of thermoresponsive poly(<I>N</I>-isopropylacrylamide)(PIPAAm) on PS nanofibrous mats. Image analysis of the PS nanofiber revealed a unimodal distribution pattern with 400 nm average fiber diameter. Graft polymerization of PIPAAm on PS nanofibrous mats was confirmed by spectroscopic methods such as ATR-FTIR, ESCA, and AFM. Human fibroblasts were cultured on four different surfaces, PIPAAm-grafted and ungrafted PS dishes and PIPAAm-grafted and ungrafted PS nanofibrous mats, respectively. Cells on PIPAAm-grafted PS nanofibrous mats were well attached, spread, and proliferated significantly much more than those on other surfaces. Cultured cells were easily detached from the PIPAAm-grafted surfaces by decreasing culture temperature to 20°C, while negligible cells were detached from ungrafted surfaces. Moreover, cells on PIPAAm-grafted PS nanofibrous mats were detached more rapidly than those on PIPAAm-grafted PS dishes. These results suggest that thermoresponsive nanofibrous mats are attractive cell culture substrates which enable rapid cell growth and recovery from the culture surface for application to tissue engineering and regenerative medicine.</P>
Effect of Kinesiology Taping for Ankle Instability in Stroke Patients
Donghwan Oh,Jaeyoung Park,Jinuk Kim 국제물리치료연구학회 2020 Journal of International Academy of Physical Ther Vol.11 No.1
Background: Ankle instability usually occurs after stroke, and contributes to unsafe walking and associated risk of falling in the affected patients. Objective: To investigate the effects of kinesiology taping (KT) on gait and balance ability (center of pressure, CoP) in patients with ankle instability after stroke. Design: One group, pre-post design. Methods: A total of 11 patients with ankle instability after stroke were enrolled. In all subjects, the gait and balance ability were assessed under 2 conditions: KT and barefoot. Gait and balance ability was assessed using GAITRite system and FDM-S platform. Results: Comparison between KT and barefoot condition, KT condition was significantly higher in velocity, cadence, step length, and stride length than barefoot condition (P<.05). KT condition was significantly lower in CoP path length and sway speed than barefoot condition (P<.05). Conclusion: KT indicated potential as a helpful method for walking and balancing ability in patients with ankle instability after stroke. Therefore, this study recommends KT as an option applicable to the stroke with ankle instability.
Oh, Seung Jae,Chhajed, Sameer,Poxson, David J,Cho, Jaehee,Schubert, E Fred,Tark, Sung Ju,Kim, Donghwan,Kim, Jong Kyu Optical Society of America 2013 Optics express Vol.21 No.1
<P>The performance enhancement of polycrystalline Si solar cells by using an optimized discrete multilayer anti-reflection (AR) coating with broadband and omni-directional characteristics is presented. Discrete multilayer AR coatings are optimized by a genetic algorithm, and experimentally demonstrated by refractive-index tunable SiO2 nano-helix arrays and co-sputtered (SiO2)x(TiO2)1?x thin film layers. The optimized multilayer AR coating shows a reduced total reflection, leading to the high incident-photon-to-electron conversion efficiency over a correspondingly wide range of wavelengths and incident angles, offering a very promising way to harvest more solar energy by virtually any type of solar cells for a longer time of a day.</P>
Migration of Sn and Pb from Solder Ribbon onto Ag Fingers in Field-Aged Silicon Photovoltaic Modules
Oh, Wonwook,Kim, Seongtak,Bae, Soohyun,Park, Nochang,Chan, Sung-Il,Kang, Yoonmook,Lee, Hae-Seok,Kim, Donghwan Hindawi Limited 2015 International journal of photoenergy Vol.2015 No.-
<P>We investigated the migration of Sn and Pb onto the Ag fingers of crystalline Si solar cells in photovoltaic modules aged in field for 6 years. Layers of Sn and Pb were found on the Ag fingers down to the edge of the solar cells. This phenomenon is not observed in a standard acceleration test condition for PV modules. In contrast to the acceleration test conditions, field aging subjects the PV modules to solar irradiation and moisture condensation at the interface between the solar cells and the encapsulant. The solder ribbon releases Sn and Pb via repeated galvanic corrosion and the Sn and Pb precipitate on Ag fingers due to the light-induced plating under solar irradiation.</P>
Evaluation of Anti-Soiling and Anti-Reflection Coating for Photovoltaic Modules
Oh, Wonwook,Kang, Byungjun,Choi, Sun,Bae, Soohyun,Jeong, Sujeong,Kim, Soo Min,Lee, Hae-Seok,Kim, Donghwan,Hwang, Heon,Chan, Sung-Il American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.10
<P>Areas with abundant sunlight, such as Middle Eastern deserts in Asia, are optimal sites for photovoltaic power generation. However, the average power loss of photovoltaic modules caused by soiling is 14.3% after two months of use. We evaluate the effect of a silica-based anti-soiling and anti-reflection coating for photovoltaic modules. The coating is intended to not only improve the optical transmission of the cover glass but also mitigate the performance loss due to soiling. We compare the optical properties of bare glass and the coated glass. The power of the module exhibits a 2.56% improvement on average because of the anti-reflection function. The anti-soiling effect of the coating is evaluated by in-house artificial-soiling tests. The soiling loss is mitigated by over 3.85% according to the tests. The multifunctional coating can be easily applied at room temperature using a low-cost solution through the manual coating method.</P>