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In-situ 졸-겔 법을 이용한 저가습 작동용 수소 이온 교환막 연료전지용(PEMFC) 나피온/TiO<sub>2</sub> 복합막
최범석 ( Beomseok Choi ),고영돈 ( Youngdon Ko ),김화중 ( Whajung Kim ) 한국공업화학회 2019 공업화학 Vol.30 No.1
저가습 작동을 위한 수소 이온 교환막 연료전지용 Nafion/TiO<sub>2</sub> 복합막을 졸-겔 법을 이용하여 제조하였다. 이때 Nafion 막에 TiO<sub>2</sub> 나노 입자를 함침시키기 위하여 TiO<sub>2</sub> 전구체 용액에 1일부터 7일까지 함침 시간을 달리하여 복합막을 제조 하였다. 담금 시간이 증가할수록 Nafion막 내에 함침되는 TiO<sub>2</sub> 함량이 증가하였다. TiO<sub>2</sub> 함량이 증가함에 따라 막의 표면의 친수성이 증가하면서 접촉각은 감소하는 것을 보여주었다. 물 흡수력(water uptake)과 복합막을 통한 수소 이온 전도도는 담금 시간이 4일인 경우 가장 높게 나타났고 4일 이상인 경우에는 오히려 감소하는 경향을 보여주었다. 담금 시간이 7일인 경우에는 큰 TiO<sub>2</sub> 입자들이 막의 표면과 내부에 생성되어 애노드에서 캐소드로의 수소 이온 전도를 방해하게 되는 결과를 초래하였다. 전지 성능 시험 결과 물 흡수력 및 수소 이온 전도도의 결과와 상당히 일치하는 것을 보여주었다. 즉, 0.6 V에서 담금 시간이 1일, 3일, 4일 및 7일인 경우 전류 밀도가 상대 습도(relative humidity, RH) 40%에서 각각 0.54, 0.6, 0.63 A/㎠ 및 0.49 A/㎠를 나타내었다. Nafion 분산액과 TiO<sub>2</sub> 입자를 혼합하여 제작한 막과 Nafion 115를 이용하여 RH 40%에서 수행한 전지 성능 결과와 비교할 때 졸-겔 법을 이용하여 제조한 복합막의 경우 약 66%의 전지 성능 향상을 얻을 수 있었다. Nafion/TiO<sub>2</sub> composite membranes were prepared via an in-situ sol-gel process with different immersing periods from 1 day to 7 days for the low humidifying proton exchange membrane fuel cell. As the immersing time increased, the TiO<sub>2</sub> content within the Nafion membrane increased. The contact angle decreased with the increased TiO<sub>2</sub> content in the composite membrane due to the increased hydrophilicity. The water uptake and proton conductivity reached to the highest level for 4 day immersing period, then decreased as the immersing period increased. A 7 days of immersing time was shown to be too long because too much TiO<sub>2</sub> aggregates were formed on the membrane surface as well as interior of the membrane, interfering the proton transfer from anode to cathode. Cell performance results were in good agreement with those of the water uptake and proton conductivity; current densities under a relative humidity (RH) of 40% were 0.54, 0.6, 0.63 A/㎠ and 0.49 A/㎠ for the immersing time of 1, 3, 4 and 7 days, respectively at a 0.6 V. The composite membrane prepared via the in-situ sol-gel process exhibited the enhancement in the cell performance under of RH 40% by a maximum of about 66% compared to those of using the recasting composite membrane and Nafion 115.
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Acoustofluidic Microbioreactor Using Surface Acoustic Wave-induced Acoustic Streaming Flow
Cha Beomseok,이송하,Park Gyeongmin,Ko Jeongu,Yoon Min,Park Jinsoo 한국바이오칩학회 2024 BioChip Journal Vol.18 No.2
Microbioreactors have been widely utilized as an alternative to conventional benchtop reactors, since the miniaturized platforms off er advantages including reduced sample volume and homogeneous microenvironments. Here, we proposed an acoustofl uidic microbioreactor based on surface acoustic wave (SAW)-induced acoustic streaming fl ow (ASF). The SAW- induced ASF, which originates from the wave attenuation in a fl uid, allows rapid mixing and heat transfer for enhanced mass and heat transfer within the sample fl uid. We conducted thorough numerical and experimental investigations on the acousto-hydrodynamics and heat transfer phenomena to fi nd an optimal frequency in the prescribed cylindrical microwell. We found that the homogenous chemical concentration and temperature distributions within the fl uid were rapidly achieved by the SAW-induced ASF in the proposed device. For proof-of-concept demonstration of practical applicability, we cultured Escherichia coli as a model cell using the proposed acoustofl uidic microbioreactor. From comparative evaluation with con- ventional platforms including a shaker incubator and a microplate shaker, we confi rmed that the bacteria growth rate was enhanced in the proposed acoustofl uidic microbioreactor due to the high homogeneity in the chemical concentration and temperature by the acoustic agitation, without any moving mechanical components. We expect that the proposed ASF-based microbioreactor can be broadly utilized for various biological applications that require homogeneous mixing and temperature gradient within a reaction medium.
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Radiation Dose Assessment of Thorium-containing Gas Mantle for Use and Disposal Scenarios
Jimin Shin,Beomseok Ko,Hee Seo,Meeryeong Kim,Minkyung Kim,Sangmin Lee 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
The IAEA recommended considerations for exemption regulations of consumer products containing greater amounts of radioactive isotopes than the amounts specified for generic exemption. One of the major considerations is the expected exposure dose should be less than 10 μSv/y and 1 mSv/y for general cases and low probability cases, respectively, in all predictable scenarios. Under this recommendation, many countries evaluated the radiation dose for exposure scenarios of various products in consideration of the national circumstances and, then, established their own specific exemption regulation. In Republic of Korea, the “Regulation on substances excluded from radioactive isotopes” was legislated to specify consumer products excluded from regulation. However, as the usage status and product specifications has changed over time, it is necessary to periodically verify the validity of the regulation criteria in the view of exemption justification. In this study, we developed the use and disposal scenarios in consideration of the domestic use of thorium-containing gas mantle and evaluated radiation dose of each scenario accordingly. The gas mantles are used as a wick for gas lanterns and the maximum activity of natural thorium contained among the currently available gas mantles is 12.5 kBq. Radioactive isotopes in the decay chain of natural thorium can be divided into three groups according to their physical characteristics, and exposure routes suitable for each group were considered in dose calculation. Currently, most gas mantles are installed in camping lanterns. Therefore, we developed use scenarios related to camping. The average number of camping trips and time spent at the campground were set by the data from Korea Tourism Organization. Tent sizes and vehicle specifications were determined by referring to surveys and products in Korea. The used gas mantle is disposed of in a garbage bag for general waste and transported to landfill or incinerator. We determined the amount of gas mantle discarded in landfill and incinerator by the data from Korea Environment Corporation. The exposure time and amount handled by an individual were determined by considering the number of waste collection vehicles, landfills, and incinerators. Although we assumed the maximum activity of the gas mantle for conservative evaluation, the calculated radiation doses for the use and disposal scenarios were below the general requirement (i.e., 10 μSv/y) in all scenarios.
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Artificial Intelligence in Health Care: Current Applications and Issues
박찬우,서성욱,Kang Noeul,Ko BeomSeok,Choi Byung Wook,Park ChangMin,Chang Dong Kyung,김휘영,Kim Hyunchul,이현나,Jang Jinhee,Ye Jong Chul,Jeon Jong Hong,Seo Joon Beom,Kim Kwang Joon,Jung Kyu-Hwan,Kim Namkug,Paek Se 대한의학회 2020 Journal of Korean medical science Vol.35 No.42
In recent years, artificial intelligence (AI) technologies have greatly advanced and become a reality in many areas of our daily lives. In the health care field, numerous efforts are being made to implement the AI technology for practical medical treatments. With the rapid developments in machine learning algorithms and improvements in hardware performances, the AI technology is expected to play an important role in effectively analyzing and utilizing extensive amounts of health and medical data. However, the AI technology has various unique characteristics that are different from the existing health care technologies. Subsequently, there are a number of areas that need to be supplemented within the current health care system for the AI to be utilized more effectively and frequently in health care. In addition, the number of medical practitioners and public that accept AI in the health care is still low; moreover, there are various concerns regarding the safety and reliability of AI technology implementations. Therefore, this paper aims to introduce the current research and application status of AI technology in health care and discuss the issues that need to be resolved.
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Is Heparin Effective for the Controlled Delivery of High-Dose Bone Morphogenetic Protein-2?
Kim, Ri Youn,Lee, Beomseok,Park, Si-Nae,Ko, Jae-Hyung,Kim, In Sook,Hwang, Soon Jung Mary Ann Liebert 2016 Tissue engineering. Part A Vol.22 No.9
<P>Sustained release of bone morphogenetic protein (BMP)-2 by heparin-contained biomaterials is advantageous for bone tissue regeneration using low-dose BMP-2. However, its effect with high-dose BMP-2 is still unclear and should be clarified considering the clinical use of a high dose of BMP-2 in spine and oral surgery. This study aimed to evaluate the efficacy of a heparin-conjugated collagen sponge (HCS) with high-dose BMP-2 delivery by investigating in vivo initial osteogenic regulation and bone healing over 12 weeks in comparison with that of an absorbable collagen sponge (ACS). The in vitro BMP-2 release profile in the HCS exhibited a lower burst followed by a sustained release of BMP-2, whereas that of the ACS showed an initial burst phase only. As a result of a lower burst, the HCS-BMP group showed higher expression of bone-forming/resorbing markers and enhanced activation of osteoclasts than the ACS-BMP group within the scaffold of defect after 7 days, which is presumed to be because of retention of relatively higher amounts of BMP-2. However, the surrounding calvariae were less resorbed in the HCS-BMP group, compared with the aggressive resorptive response in the ACS-BMP group. Microcomputed tomography and histology revealed that HCS-BMP guided more effective bone regeneration of central defect over time inducing minor ossification at the defect exterior, whereas ACS-BMP exhibited excessive ossification at the defect exterior. These results showed that HCS-mediated BMP-2 delivery at a high dose has advantages over ACS, including less early resorption of surrounding bone tissue and higher efficacy in compact bone regeneration over a longer period, highlighting a clinical feasibility of this technology.</P>
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