The effects of operating temperature on Field Effect Transistor Gas Sensor with In₂O₃ sensing layer

Wonjun Shin,Gyuweon Jung,Yujeong Jeong,Seongbin Hong,Jinwoo Park,Yoonki Hong,Byung-Gook Park,Jong-Ho Lee 대한전자공학회 2019 대한전자공학회 학술대회 Vol.2019 No.6

Inhibitory effect of celastrol on adipogenic differentiation of human adipose-derived stem cells

Hong, Wonjun,Park, Junghyun,Yun, Wonjin,Kang, Phil Jun,Son, Daryeon,Jang, Jihoon,Kim, In Yong,You, Seungkwon Elsevier 2018 Biochemical and biophysical research communication Vol. No.

<P><B>Abstract</B></P> <P>Control of adipogenesis in mesenchymal stem cells (MSCs) offers enormous potential for management of obesity- and aging-related diseases. Celastrol, the traditional Chinese medicine extracted from <I>Tripterygium wilfordi</I>, exhibits anti-obesity effects in <I>in vitro</I> and <I>in vivo</I> murine models. This study describes how celastrol affects multilineage differentiation potential of human adipose-derived stem cells (hADSCs). We performed <I>in vitro</I> adipogenic differentiation of hADSCs and investigated how celastrol-induced lipid accumulation and expression of adipocyte differentiation markers varied with dose, duration, and donor age. In addition, we assessed the effect of celastrol on osteogenic and chondrogenic differentiation of hADSCs. During adipogenic induction of hADSCs, the inhibitory effect of celastrol on lipid accumulation and adipogenesis depended on dose, duration, time of administration, and individual donor. Inhibition was mediated by proliferator-activated receptor-γ (PPARG) and CCAAT/enhancer-binding protein alpha (CEBPA). Celastrol also suppressed differentiation of hADSCs into the osteogenic and chondrogenic lineages. Celastrol plays a regulatory role in multilineage differentiation of human MSCs. Our findings provide important insights regarding management of obesity and stem cell therapy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Celastrol has therapeutic potential against obesity- and aging-related diseases. </LI> <LI> Anti-adipogenic effect of celatrol in human ADSCs depended on dose and duration. </LI> <LI> Celatrol inhibited adipogenesis in human ADSCs by regulating <I>PPARG</I> and <I>CEBPA.</I> </LI> <LI> Celastrol inhibited adipogenesis in hADSCs derived from 12 donors with various ages. </LI> <LI> Celastrol also inhibited osteogenic and chondrogenic differentiation in hADSCs. </LI> </UL> </P>

MMS 점군 데이터를 이용한 CCTV의 실질적 감시영역 추출

최원준 ( Wonjun Choi ),박소연 ( Soyeon Park ),최윤조 ( Yoonjo Choi ),홍승환 ( Seunghwan Hong ),김남훈 ( Namhoon Kim ),손홍규 ( Hong-gyoo Sohn ) 대한원격탐사학회 2021 大韓遠隔探査學會誌 Vol.37 No.5

스마트 시티 서비스 중 방범·방재 분야가 2018년 기준 가장 높은 24%를 차지하고 있으며, 실시간 상황정보제공에 가장 중요한 플랫폼은 CCTV(Closed-Circuit Television) 이다. 이러한 CCTV의 활용을 극대화 하기 위해서는 CCTV가 제공하는 실질적인 감시 영역을 파악하는 것이 필수적이다. 하지만 국내에 설치된 CCTV양은 지자체 관리대상 포함 100만대를 넘고 있다. 이러한 방대한 양의 CCTV의 가시영역을 수동적으로 파악해야 하는 것은 문제점으로 제기되고 있다. 이에 본 연구에서는 CCTV의 실질적 가시권 영역 데이터를 효율적으로 구축하고, 관리자가 상황 파악에 소요되는 시간을 단축하는 방안을 제시하고자 하였다. 이를 위하여 첫째, 접근이 어려운 기 설치된 CCTV 카메라의 외부표정요소와 초점 거리를 MMS(Mobile Mapping System)의 점군 데이터를 활용하여 계산하고, 이 결과를 활용하여 FOV(Field of View)를 계산하였다. 둘째, 첫 단계에서 계산된 FOV 결과를 이용하여 건물에 의하여 발생하는 폐색 영역을 고려하여 CCTV의 실질적 감시 영역을 그리드 단위 1 m, 2 m, 3 m, 5 m, 10 m 폴리곤 데이터로 구축하였다. 이 방법을 경상북도 울진군에 위치한 5개소의 CCTV 영상에 적용한 결과, 평균 재투영 오차는 약 9.31 pixel, 공공데이터포털(Data Portal)에서 제공하는 위·경도 좌표와의 거리는 평균 약 10 m의 거리 차이가 발생하였고, MMS를 통해 취득한 점군 데이터 상의 CCTV 위치 좌표 값과는 평균 약 1.688 m의 위치 차이를 나타냈다. 단위 그리드의 한 변의 크기가 3 m인 경우, 본 연구를 통하여 계산된 감시 영역 폴리곤은 육안으로 확인한 실제 감시 영역과 최소 70.21%에서 최대 93.82%까지 일치함을 확인할 수 있었다. Among smart city services, the crime and disaster prevention sector accounted for the highest 24% in 2018. The most important platform for providing real-time situation information is CCTV (Closed-Circuit Television). Therefore, it is essential to create the actual CCTV surveillance coverage to maximize the usability of CCTV. However, the amount of CCTV installed in Korea exceeds one million units, including those operated by the local government, and manual identification of CCTV coverage is a time-consuming and inefficient process. This study proposed a method to efficiently construct CCTV’s actual surveillance coverage and reduce the time required for the decision-maker to manage the situation. For this purpose, first, the exterior orientation parameters and focal lengths of the pre-installed CCTV cameras, which are difficult to access, were calculated using the point cloud data of the MMS (Mobile Mapping System), and the FOV (Field of View) was calculated accordingly. Second, using the FOV result calculated in the first step, CCTV’s actual surveillance coverage area was constructed with 1 m, 2 m, 3 m, 5 m, and 10 m grid interval considering the occluded regions caused by the buildings. As a result of applying our approach to 5 CCTV images located in Uljin-gun, Gyeongsnagbuk-do the average re-projection error was about 9.31 pixels. The coordinate difference between calculated CCTV and location obtained from MMS was about 1.688 m on average. When the grid length was 3 m, the surveillance coverage calculated through our research matched the actual surveillance obtained from visual inspection with a minimum of 70.21% to a maximum of 93.82%.

Hybrid ionogel electrolytes with POSS epoxy networks for high temperature lithium ion capacitors

Na, Wonjun,Lee, Albert S.,Lee, Jin Hong,Hong, Soon Man,Kim, Eunkyoung,Koo, Chong Min North-Holland Pub. Co 2017 Solid state ionics Vol.309 No.-

<P><B>Abstract</B></P> <P>Thermally curable hybrid ionogel electrolytes consisting of epoxy-functionalized POSS, amine-terminated polypropylene glycol, and ionic liquid electrolyte, 1M LiTFSI in BMPTFSI were fabricated to give ionic conducting epoxy networks with cubic inorganic star networks crosslinked with lithium ion dissociating polypropylene glycol linkers. Characterization of these hybrid ionogels revealed high ion conduction, exceptional thermal stability, and electrochemical stability. Lithium ion capacitors fabricated with these hybrid ionogels revealed exceptional performance on par with the neat liquid ionic liquid electrolyte, and far superior over ionogels fabricated with conventional organic crosslinkers, due to the mechanical robustness and lithium ion dissociative character imparted by the POSS and PPG functionalities.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hybrid ionogel electrolytes with POSS epoxy networks were fabricated. </LI> <LI> Quasi solid state behavior was confirmed through rheological analysis. </LI> <LI> High ion conduction, good thermal and electrochemical stability were observed. </LI> <LI> Lithium ion capacitors fabricated with hybrid ionogels revealed good performance. </LI> </UL> </P>

A Study on Decoding Models for the Reconstruction of Hand Trajectories from the Human Magnetoencephalography

Yeom, Hong Gi,Hong, Wonjun,Kang, Da-Yoon,Chung, Chun Kee,Kim, June Sic,Kim, Sung-Phil Hindawi Publishing Corporation 2014 BioMed research international Vol.2014 No.-

<P>Decoding neural signals into control outputs has been a key to the development of brain-computer interfaces (BCIs). While many studies have identified neural correlates of kinematics or applied advanced machine learning algorithms to improve decoding performance, relatively less attention has been paid to optimal design of decoding models. For generating continuous movements from neural activity, design of decoding models should address how to incorporate movement dynamics into models and how to select a model given specific BCI objectives. Considering nonlinear and independent speed characteristics, we propose a hybrid Kalman filter to decode the hand direction and speed independently. We also investigate changes in performance of different decoding models (the linear and Kalman filters) when they predict reaching movements only or predict both reach and rest. Our offline study on human magnetoencephalography (MEG) during point-to-point arm movements shows that the performance of the linear filter or the Kalman filter is affected by including resting states for training and predicting movements. However, the hybrid Kalman filter consistently outperforms others regardless of movement states. The results demonstrate that better design of decoding models is achieved by incorporating movement dynamics into modeling or selecting a model according to decoding objectives.</P>

Lithium Dendrite Suppression with UV-Curable Polysilsesquioxane Separator Binders

Na, Wonjun,Lee, Albert S.,Lee, Jin Hong,Hwang, Seung Sang,Kim, Eunkyoung,Hong, Soon Man,Koo, Chong Min American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.20

<P>For the first time, an inorganic organic hybrid polymer binder was used for the coating of hybrid composites on separators to enhance thermal stability and to prevent formation of lithium dendrite in lithium metal batteries. The fabricated hybrid-composite-coated separators exhibited minimal thermal shrinkage compared with the previous composite separators (<5% change in dimension), maintenance of porosity (Gurley number 400 s/100 cm(3)), and high ionic conductivity (0.82 mS/cm). Lithium metal battery cell examinations with our hybrid-composite -coated separators revealed excellent C-rate and cyclability performance due to the prevention of lithium dendrite growth on the lithium anode even after 200 cycles under 0.2-5C (charge discharge) conditions. The mechanism for lithium dendrite prevention was attributed to exceptional nanoscale surface mechanical properties of the hybrid composite coating layer compared with the lithium metal anode, as the elastic modulus of the hybrid-composite-coated separator far exceeded those of both the lithium metal anode and the required threshold for lithium metal dendrite prevention.</P>

High Temperature Lithium Ion Capacitors Fabricated with PEO functionalized Polysilsesquioxane Ionogel Polymer Electrolytes

Wonjun Na,Albert S. Lee,Jin Hong Lee,Eunkyoung Kim,Chong Min Koo 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Binder-less chemical grafting of SiO₂ nanoparticles onto polyethylene separators for lithium-ion batteries

Na, Wonjun,Koh, Ki Hwan,Lee, Albert S.,Cho, Sangho,Ok, Byoeri,Hwang, Suk-Won,Lee, Jin Hong,Koo, Chong Min Elsevier 2019 Journal of membrane science Vol.573 No.-

<P><B>Abstract</B></P> <P>Silica nanoparticles were chemically grafted onto a porous polyethylene separator to improve the adhesion strength, thermal stability, and electrochemical performance of a polyolefin separator. A surface activation via UVO plasma treatment, followed by silane hybridization yielded a polymeric binder-free, thin coating of SiO<SUB>2</SUB> nanoparticles onto the separator. The chemical grafting provided a much stronger adhesive strength (> 2.5 N/cm), reduced thermal shrinkage (< 5% at 120 °C), and higher ionic conductivity (0.84 mS/cm) than conventional physical coating of a ceramic particle-based polymer composite. Lithium-ion batteries fabricated with metallic lithium as the anode, a LiFePO<SUB>4</SUB> (LFP) cathode and SiO<SUB>2</SUB>-grafted separator showed an excellent rate capability (68 mAh/g at 5 C) and cycling performance (143 mAh/g after 200 cycles).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Binder-free silica-grafted PE separator was fabricated for the first time. </LI> <LI> Silica grafting improved adhesion strength, mechanical property of separator. </LI> <LI> Silica-grafted separator effectively enhanced the wettability to the electrolyte. </LI> <LI> Silica-grafted separator revealed strong thermal stability and good battery performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

유량 변화에 따른 원자층 증착 장비 내부 유동특성 연구

최원준(Wonjune Choe),홍경표(Kyung Pyo Hong),최예린(Yerin Choi),김문기(Moon Ki Kim),최재붕(Jae Boong Choi),이태린(Tae-Rin Lee),김형근(Hyeongkeun Kim) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11

Effect of Underlying Comorbidities on the Infection and Severity of COVID-19 in Korea: a Nationwide Case-Control Study

Ji Wonjun,Huh Kyungmin,Kang Minsun,Hong Jinwook,Bae Gi Hwan,이예린,Na Yewon,Choi Hyoseon,Gong Seon Yeong,Choi Yoon-Hyeong,Ko Kwang-Pil,Im Jeong-Soo,정재훈 대한의학회 2020 Journal of Korean medical science Vol.35 No.25

Background: The coronavirus disease 2019 (COVID-19) pandemic is an emerging threat worldwide. It remains unclear how comorbidities affect the risk of infection and severity of COVID-19. Methods: This is a nationwide retrospective case-control study of 219,961 individuals, aged 18 years or older, whose medical costs for COVID-19 testing were claimed until May 15, 2020. COVID-19 diagnosis and infection severity were identified from reimbursement data using diagnosis codes and on the basis of respiratory support use, respectively. Odds ratios (ORs) were estimated using multiple logistic regression, after adjusting for age, sex, region, healthcare utilization, and insurance status. Results: The COVID-19 group (7,341 of 219,961) was young and had a high proportion of female. Overall, 13.0% (954 of 7,341) of the cases were severe. The severe COVID-19 group had older patients and a proportion of male ratio than did the non-severe group. Diabetes (odds ratio range [ORR], 1.206–1.254), osteoporosis (ORR, 1.128–1.157), rheumatoid arthritis (ORR, 1.207–1.244), substance use (ORR, 1.321–1.381), and schizophrenia (ORR, 1.614–1.721) showed significant association with COVID-19. In terms of severity, diabetes (OR, 1.247; 95% confidential interval, 1.009–1.543), hypertension (ORR, 1.245–1.317), chronic lower respiratory disease (ORR, 1.216–1.233), chronic renal failure, and end-stage renal disease (ORR, 2.052–2.178) were associated with severe COVID-19. Conclusion: We identified several comorbidities associated with COVID-19. Health care workers should be more careful while diagnosing and treating COVID-19 when patients have the abovementioned comorbidities.