농경지 비점오염원 관리를 통한 탄소중립 효과 및 하천의 수질개선 방안에 관한 연구

박기학(Kihak Park),어성욱(SeongWook Oa),김서현(Seohyun Kim),김극태(Keugtae Kim) 한국방재학회 2022 한국방재학회논문집 Vol.22 No.6

우리나라는 2050 탄소중립 선언 이후 농축수산부문은 ’50년까지 ’18년(24.7백만톤) 대비 37.7% 감축한 15.4백만톤 배출을 목표로 하고 있다. 이에 따라 농업분야에서는 화학비료의 사용을 저감하고, 토양의 질소배출량을 줄여 온실가스를 줄이고자 노력하고 있다. 본 연구에서는 논의 벼농사 이후에 조사료 재배시 추가적인 비료투입 없이 생산할 경우 온실가스 저감 및 수질개선의 효과를 분석하였다. 조사료 재배시 온실가스 감축 효과는 10 a (1,000 m2) 당 비료 237 kgCO2-eq/1,000m2, 작물보호제 4 kgCO2-eq/1,000m2로 전체 저감량은 241 kgCO2-eq/1,000m2로 분석되었다. 이는 겉보리 재배시 성분별 비료량은 1,000 m2 당 질소 62.90 kg, 인 22.83 kg, 칼륨 19.31 kg이 투입되는 양을 기준으로 산정하였다. 또한, 토양의 비료 사용 절감으로 인해 약 25.47 kgPO43--eq의 부영양화를 저감시키는 것으로 분석되었다. 조사료의 재배 확대로 인해 비점오염원인 농경지로부터 하천의 부영양화를 저감시킬 수 있을 것으로 예측된다. In Korea, the carbon emission from the agricultural, livestock, and fishery sectors were 24.7 million tCO2-eq in 2018. Following the 2050 carbon neutral declaration, the total carbon emissions from these sectors are expected to decrease to 15.4 million tCO2-eq by 2050, a reduction of 37.7%. Therefore, efforts are being made to reduce the use of chemical fertilizers, soil nitrogen emissions, and greenhouse gases in the agricultural sector. In this study, we analyzed the effects of irradiation charges on greenhouse gas reduction and water quality improvement after rice cultivation without the addition of any fertilizer. The greenhouse gas emission for fertilizer during irradiation cultivation was estimated to be 237 kgCO2-eq/1,000m2, 4 kgCO2-eq/1,000m2 less than that by using a crop protection agent (241 kgCO2-eq/1,000m2). The measurement was based on the amount of nitrogen, phosphorus, and potassium (62.90, 22.83, and 19.31 kg, respectively) per 1,000 m2 barley cultivation. In addition, a reduction in fertilizer use was estimated to reduce eutrophication by approximately 25.47 kgPO43--eq. Thus, the eutrophication of rivers from farmland, a nonpoint pollution source, is predicted to reduce by expanding irradiation cultivation.

Heparin-hyaluronic acid hydrogel in support of cellular activities of 3D encapsulated adipose derived stem cells

Gwon, Kihak,Kim, Eunsol,Tae, Giyoong Elsevier 2017 ACTA BIOMATERIALIA Vol.49 No.-

<P><B>Abstract</B></P> <P>We have developed stem cell-responsive, heparin-hyaluronic acid (Hep-HA) hydrogel, crosslinked by thiolated heparin (Hep-SH) and methacrylated hyaluronic acid (HA-MA) <I>via</I> visible light mediated, thiol-ene reaction. Physical properties of the hydrogel (gelation time, storage modulus, and swelling ratio) were tunable by adjusting light intensity, initiator/polymer concentration, and precursor pH. Culture of human adipose derived mesenchymal stem cells (ADSCs) using this hydrogel was characterized and compared with the control hydrogels including Hep-PEG hydrogel, PEG-HA hydrogel. Sufficient initial adhesion and continuous proliferation of ADSCs in 2D were observed on both heparin-containing hydrogels (Hep-HA and Hep-PEG hydrogel) in contrast to no adhesion of ADSCs on PEG-HA hydrogel. On the other hand, in the case of 3D culture of encapsulated ADSCs, efficient cellular activities such as spreading, proliferation, migration, and differentiation of ADSCs were only observed in soft Hep-HA hydrogel compared to Hep-PEG or PEG-HA hydrogel with the similar modulus. The upregulated expressions of hyaluronidases in ADSCs encapsulated in Hep-HA hydrogel compared to the control hydrogels and effective degradation of the hydrogel by hyaluronidase imply that the degradation of hydrogel was necessary for 3D cellular activities. Thus, Hep-HA hydrogel, where heparin acts as a binding domain for ADSCs and HA acts as a degradation site by cell secreted enzymes, was efficient for 3D culture of human ADSCs without any additional modification using biological/chemical molecules.</P> <P><B>Statement of Significance</B></P> <P>Stem cell-responsive hydrogel composed of heparin and hyaluronic acid was prepared by visible light-mediated thiol-ene reaction. Without additional modification using functional peptides for cell adhesion and matrix degradation, ADSCs encapsulated in this hydrogel showed efficient cellular activities such as spreading, proliferation, migration, and differentiation of ADSCs whereas control hydrogels missing heparin or hyaluronic acid could not support cellular activities in 3D. In this hydrogel, heparin mainly acts as a binding domain for stem cells and hyaluronic acid mainly acts as a degradation site by ADSC secreted enzymes, but interrelated synergistic functions of heparin and HA were observed. Therefore, we speculate that this hydrogel can serve as a promising carrier for stem cell based therapy and various tissue engineering applications.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

지역특성을 고려한 지진재해 지역안전도 평가기술 개발사업

이기학(Kihak Lee) 대한토목학회 2023 대한토목학회지 Vol.71 No.7

Disposable Strip-Type Biosensors for Amperometric Determination of Galactose

Gwon, Kihak,Lee, Seonhwa,Nam, Hakhyun,Shin, Jae Ho The Korean Electrochemical Society 2020 Journal of electrochemical science and technology Vol.11 No.3

A development of disposable strip-type galactose sensor for point-of-care testing (POCT) was studied, which was constructed using screen-printed carbon electrodes. Galactose levels were determined by the redox reaction of galactose oxidase in the presence of potassium ferricyanide as an electron transfer mediator in a small sample volume (i.e., less than 1 µL). The optimal performance of biosensor was systematically designated by varying applied potential, operating pH, mediator concentration, and amount of enzyme on the electrode. The sensor system was identified as a highly active for the galactose measurement in terms of the sensitivity (slope = 4.76 ± 0.05 nA/µM) with high sensor-to-sensor reproducibility, the linearity (R² = 0.9915 in galactose concentration range from 0 to 400 µM), and response time (t_95% = <17 s). A lower applied potential (i.e., 0.25 V vs. Ag/AgCl) allowed to minimize interference from readily oxidizable metabolites such as ascorbic acid, acetaminophen, uric acid, and acetoacetic acid. The proposed galactose sensor represents a promising system with advantage for use in POCT.

Improved near infrared-mediated hydrogel formation using diacrylated Pluronic F127-coated upconversion nanoparticles

Gwon, Kihak,Jo, Eun-Jung,Sahu, Abhishek,Lee, Jae Young,Kim, Min-Gon,Tae, Giyoong Elsevier 2018 Materials science & engineering. C, Materials for Vol.90 No.-

<P><B>Abstract</B></P> <P> <I>In situ</I> hydrogel synthesis based on photopolymerization has been recognized as a promising strategy that can be used for tissue augmentation. In this study, we developed an efficient <I>in situ</I> gelation method to prepare bulk hydrogels <I>via</I> near infrared (NIR)-mediated photopolymerization using acrylated polyethylene glycol and diacrylated Pluronic F127-coated upconversion nanoparticles (UCNPs). In our system, upon 980-nm laser irradiation, UCNPs transmit visible light, which triggers the activation of eosin Y to initiate polymerization. We found that the UCNPs coated with diacrylated Pluronic F127 can enhance the photopolymerization efficiency and thus enable the production of bulk hydrogel with requirement of a lower NIR light power compared to that required with the bare UCNPs. This photopolymerization approach will be beneficial to achieve <I>in situ</I> polymerization <I>in vivo</I> for various biomedical applications such as cell/drug delivery and construction of tissue augments.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We developed an efficient bulk-sized <I>in situ</I> gelation method via NIR-mediated photopolymerization using UCNPs. </LI> <LI> UCNPs convert NIR irradiation into visible light to activate the initiator. </LI> <LI> Diacrylated Pluronic F127-coated UCNPs can enhance photopolymerization efficiency. </LI> <LI> This NIR-mediated <I>in situ</I>-forming hydrogels have the potential for biomedical applications. </LI> </UL> </P>

하수처리시설의 에너지자립화 및 경제적 효과분석

박기학 ( Kihak Park ),이호식 ( Hosik Lee ),하준수 ( Junsu Ha ),김극태 ( Keugtae Kim ),임채승 ( Chaeseung Lim ) 한국물환경학회(구 한국수질보전학회) 2021 한국물환경학회지 Vol.37 No.2

It is generally known that a wastewater treatment plant (WWTP) consumes immense energy even if it can produce energy. With an aim to increase the energy independence rate of WWTP from 3.5% in 2010 to 50% in 2030, the Korean government has invested enormous research funds. In this study, cost-effective operating alternatives were investigated by analyzing the energy efficiency and economic feasibility for biogas and power generation using new and renewable energy. Based on the US EPA Energy Conservation Measures and Korea ESCO projects, energy production and independence rate were also analyzed. The main energy consumption equipment in WWTP is the blower for aeration, discharge pump for effluent, and pump for influent. Considering the processes of WWTP, the specific energy consumption rate of the process using media and MBR was the lowest (0.549 kWh/m³) and the highest (1.427 kWh/m³), respectively. Energy-saving by enhancing anaerobic digester efficiency was turned out to be efficient when in conjunction with stable wastewater treatment. The result of economic analysis (B/C ratio) was 2.5 for digestive gas power generation, 0.86 for small hydropower, 0.49 for solar energy, and 0.15 for wind energy, respectively. Furthermore, it was observed that the energy independence rate could be enhanced by installing energy production facilities such as solar and small hydropower and reducing energy consumption via the replacement of high-efficiency operating.

A Preliminary Development of the K-DEMO Divertor Concept

Im, Kihak,Kwon, Sungjin,Park, Jong Sung Institute of Electrical and Electronics Engineers 2016 IEEE transactions on plasma science Vol. No.

<P>A preconceptual design study for the Korean fusion demonstration tokamak reactor (K-DEMO) has been started in 2012. The results of the preliminary concept study on the K-DEMO divertor are summarized in this paper. An up-down symmetric double-null configuration is selected as a primary choice for study with high elongation of 2 and the triangularity of 0.625. For the vertical maintenance of the K-DEMO in-vessel components, upper and lower divertors are subdivided into 32 toroidal modules, respectively. With maintaining its functionality, the poloidal coverage of divertor is restricted to maximize the breeding area of blanket. The plasma radiation from the core and the edge plasma and the fusion neutron wall loading onto the first walls of the in-vessel components were calculated as heat sources to the structures of the invessel components. The divertor targets are tilted at similar to 10 degrees against separatrix field line to handle the conceived engineering limit of steady 10 MW/m(2) of peak heat flux with similar to 50% of core plasma radiation and similar to 85% of divertor plasma radiation. Divertor adopts tungsten monoblock targets, reduced activation steel-based structures carrying the pressurized water coolant. Also, the preliminary electromagnetic force extrapolated from the ITER disruption events was considered as a mechanical load to the structures in addition to the coolant pressure. The developed concept on the target and structure is supported by preliminary thermohydraulic and structural analyses using ANSYS, which show that the temperature and the stresses are within their allowables.</P>

학회 연구위원회 및 연구전문위원회의 소개와 활동

이기학(Kihak Lee),문재흠(Jae Heum Moon),홍건호(Geon Ho Hong) 한국콘크리트학회 2019 콘크리트학회지 Vol.31 No.3

A biocompatible method of controlled retrieval of cell-encapsulating microgels from a culture plate

Gwon, Kihak,Kim, Mihye,Tae, Giyoong Oxford University Press 2014 Integrative biology Vol.6 No.6

<P>We report a biocompatible method of selectively retrieving 3-D cell-encapsulating hydrogel microstructures from a culture substrate. First, poly(l-lysine)/hyaluronic acid (PLL/HA) polyelectrolyte multilayers (PEMs) with methacrylated chitosan (GMA-Chi) on top were formed on an ITO substrate. Then, a cell-encapsulating hydrogel micropattern was formed; a HepG2 cell-encapsulating heparin-based hydrogel micropattern was fabricated by thiol-ene photopolymerization. The application of an oxidative potential of 2 V resulted in the detachment of the cell-encapsulating hydrogels by the dissolution of PEMs. The time of complete retrieval of the hydrogels was controllable by modulating the number of PEM layers. The applied potential did not affect the viability or the function of the cells in the entire hydrogels. In contrast, when a reductive electrochemical potential (-1.8 V) was applied to a silane-modified ITO to release cell-encapsulating hydrogels by the desorption of silane [Chem. Commun., 2009, 5865], extensive cell death at the bottom of the hydrogel adjacent to the electrode was observed.</P>

하수 및 정수처리시설 디지털트윈 시뮬레이터 운영관리를 위한 의사결정항목 분석

박기학(Park, Kihak),김서현(Kim, Seohyun),김극태(Kim, Keugtae) 한국방재학회 2021 한국방재학회논문집 Vol.21 No.6

본 연구는 CPS 연계 하수 및 정수처리시설 시뮬레이터의 운영관리 의사결정항목을 도출하기 위한 것으로 AHP 기법을 활용하여 하수 및 정수처리 분야 전문가를 대상으로 운영요인에 대한 영향인자별 중요도를 평가하였다. 하수 및 정수처리 분야 전문가 67인(하수처리 37인, 정수처리 30인)을 대상으로 일관성 비율을 고려한 설문지를 이용하여 주요한 영향인자를 도출하였다. 의사결정을 위한 분석요소는 유입수 수질부하, 반응조 용량, 처리공정, 고탁수 유입 등의 발생가능성, 위험도, 시급성, 대응 및 복구의 상대적 중요도를 분석 도출하였다. 하수처리시설은 유입수의 수질부하 변동이 가장 주요한 운영요소로 분석되었으며, 영향인자로는 발생가능성이 주요한 항목으로 나타났다. 정수처리시설의 경우 고탁수 유입이 주요한 운영요인으로 나타났으며, 영향인자로는 발생가능성, 위험도 순으로 나타났다. 이러한 결과를 반영하여 주요 영향인자인 유입수의 변동을 파악하고, 이를 디지털트윈 시뮬레이터 구축과 연계하여 조기에 운영인자를 조절함으로써 안정적인 하수 및 정수 처리시스템에 이바지할 것으로 기대된다. This paper addresses the derivation of decision-making factors for the operation and management of the Cyber Physical systems (CPS)-linked wastewater treatment plants (WWTPs) and drinking water treatment plants (DWTPs) simulator. The analytical hierarchy process (AHP) method was applied to evaluate the importance of each influencing factor on the operational elements targeting experts. Here, the experts were 37 people working for WWTPs and 30 people working for DWTPs, respectively. The analysis factors for decision-making were influent load, reactor capacity, treatment process, occurrence of high turbidity influent, risk, urgency, response, and recovery, and their relative importance was analyzed. Among the operational elements of WWTPs, influent fluctuations have been shown as the most important factor. Conversely, the possibility of occurrence was found to be the most important influencing factor. In the case of DWTPs, the inflow of high turbidity was found to be the main operating factor, and the influencing factors were the probability of occurrence and the degree of risk. Based upon the results obtained, this study is expected to contribute to the establishment of a stable system of both WWTPs and DWTPS by identifying influent fluctuations, which are a major influencing factor, and by controlling operation factors connected with the establishment of a digital twin simulation.