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Metal-organic frameworks-driven ZnO-functionalized carbon nanotube fiber for NO<sub>2</sub> sensor
( Sungyoon Woo ),( Mingyeong Jo ),( Joon-seok Lee ),( Seung-ho Choi ),( Sungju Lee ),( Hyeon Su Jeong ),( Seon-jin Choi ) 한국센서학회 2021 센서학회지 Vol.30 No.6
In this study, heterogeneous ZnO/CNTF composites were developed to improve the NO<sub>2</sub>-sensing response, facilitated by the selfheating property. Highly conductive and mechanically stable CNTFs were prepared by a wet-spinning process assisted by the liquid crystal (LC) behavior of CNTs. Metal-organic frameworks (MOFs) of ZIF-8 were precipitated on the surface of the CNTF (ZIF-8/ CNTF) via one-pot synthesis in solution. The subsequent calcination process resulted in the formation of the ZnO/CNTF composites. The calcination temperatures were controlled at 400, 500, and 600℃ in an N<sub>2</sub> atmosphere to confirm the evolution of the microstructures and NO<sub>2</sub>-sensing properties. Gas sensor characterization was performed at 100℃ by applying a DC voltage to induce Joule heating through the CNTF. The results revealed that the ZnO/CNTF composite after calcination at 500℃ (ZnO/CNTF-500) exhibited an improved response (R<sub>air</sub>/R<sub>gas</sub> = 1.086) toward 20 ppm NO<sub>2</sub> as compared to the pristine CNTF (R<sub>air</sub>/R<sub>gas</sub> = 1.063). Selective NO<sub>2</sub>-sensing properties were demonstrated with negligible responses toward interfering gas species such as H<sub>2</sub>S, NH<sub>3</sub>, CO, and toluene. Our approach for the synthesis of MOF-driven ZnO/CNTF composites can provide a new strategy for the fabrication of wearable gas sensors integrated with textile materials.
Sungyoon Joung,Chung-Woo Lee,최윤선,김선미,Seokwon Park,Eunshik Mo,Jaehyun Park,신지인,Hyunjin Lee,박홍석 대한가정의학회 2020 Korean Journal of Family Medicine Vol.41 No.6
Background: This study aimed to explore the time interval distribution pattern between the Physicians Order for Life-Sustaining Treatment (POLST) form completion and death at a tertiary hospital in South Korea. It also examined the association between various independent parameters and POLST form completion timing. Methods: A total of 150 critically ill patients admitted to Korea University Guro Hospital between June 1, 2018 and December 31, 2018 who completed the POLST form were retrospectively analyzed and included in this study. Data were analyzed with descriptive statistics, and group comparisons were performed using the chi-square test for categorical variables. Fisher’s exact test was also used to compare cancer versus non-cancer groups. Results: More than half the decedents (54.7%) completed their POLST within 15 days of death and 73.4% within 30 days. The non-cancer group had the highest percentage of patients (77.8%) who died within 15 days of POLST form completion while the colorectal (39.1%) and other cancer (37.5%) groups had the lowest (P=0.336). Conclusion: Our findings demonstrated a current need for more explicit guidance to assist physicians with initiating more timely, proactive end-of-life discussions.
Deoiling hydrocyclone의 성능예측을 위한 수치해석 기법정립
최성윤(Sungyoon Choi),이원두(Weondoo Lee),우경진(Kyoungjin Woo),김동관(Dongkwan Kim),임재호(Jaeho Lim) 한국전산유체공학회 2014 한국전산유체공학회 학술대회논문집 Vol.2014 No.5
해양 플랜트의 생산공정 중 발생되는 부산물 중의 하나로 생산수 (Produced Water)를 들 수 있다. 생산수는 일정 처리과정을 거쳐 해양으로 배출되게 된다. 해당 처리에는 생산수 처리시스템 (PWTS, Produced Water Treatment System)이 활용되며, PWTS는 일반적으로 deoiling 하이드로 사이클론 (hydrocyclone)과 degassing drum으로 구성된다. 생산수 처리의 대부분의 역할을 하이드로 사이클론에서 담당하게 되고, 따라서 하이드로 사이클론의 효율이 PWTS 효율에 큰 영향을 미치게 된다. 현재까지 고체와 액체 혹은 기체를 분리하기 위한 하이드로 사이클론의 해석 기법 정립을 위한 다수의 연구들이 진행되었다. 본 연구에서는 deoiling 하이드로 사이클론의 성능을 비교적 정확하게 예측하는 해석 기법에 대한 연구를 진행하여 기존의 실험적 연구 결과와 유사한 결과를 확보할 수 있는 해석기법을 정립하였다.
우남섭(NamSub Woo),박종명(JongMyoung Park),권재기(JaeKi Kwon),김영주(YoungJu Kim),김상식(SangShik Kim),정성윤(SungYoon Jung) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Subsea separation is an emerging technology that requires new and optimized solutions. Subsea separation system should be reliable to ensure successful operation in a wide range of 3-phase flow regimes, without need for maintenance. Separating gas, oil, water, and sand at the seabed has great economic potential for many subsea field developments. A subsea separator can avoid or simplify costly surface platforms or floating vessels, as well as being an efficient tool to enhance hydrocarbon production. One solution of interest is the separation and re-injection of water at the seabed to avoid bringing the water up to the surface facility. In this study, subsea separation system and its foreign and domestic development status are introduced.
A Multiband Reconfigurable Power Amplifier for UMTS Handset Applications
Unha Kim,Sungyoon Kang,Jungrin Woo,Youngwoo Kwon,Junghyun Kim Professional Technical Group on Microwace Theory a 2012 IEEE Transactions on Microwave Theory and Techniqu Vol. No.
<P>A new practical reconfigurable output network for a multiband reconfigurable power amplifier (PA) is proposed for universal mobile telecommunications system (UMTS) handset applications. The proposed reconfigurable network can reconfigure the output power and the output path, as well as the frequency. It consists of a power-reconfigurable network, a frequency-reconfigurable network, and a path-selection network. In this paper, its reconfiguration principle is described to extract key design parameters for the reconfigurable PA implementation. To demonstrate the performance of the proposed structure, a 5 mm × 6 mm multiband reconfigurable PA module is developed for UMTS high- and low-frequency band application. The fabricated PA module can cover any three bands out of five popular high- and low-frequency UMTS bands. To enhance the efficiency during low output power operation, the authors' stage-bypass technique is also employed. The fabricated PA module showed adjacent channel leakage ratios better than -39 dBc up to the rated linear output power and power-added efficiencies of higher than 39% at <I>P</I><SUB>out</SUB>=28 dBm over all the UMTS frequency bands. Efficiency degradation was limited to less than 2% compared to the single-band PA. Measured RF performance of the reconfigurable PA validates the usefulness of the proposed reconfigurable structure for multiband UMTS applications.</P>
Kyeongjea Lee,Tae -Woo Kim,Sungyoon Cho,Ki-Won Kwon,DongKuKim 한국인터넷정보학회 2024 KSII Transactions on Internet and Information Syst Vol.18 No.4
Maritime activities are on the rise, there is a growing demand for high-quality communication services that can cover larger areas. However, the transmission of high data rates to maritime users is challenging due to path loss from land base stations, which limits the transmission power. To overcome this challenge, researchers have been exploring the use of buoys in a marine environment as relays for communication technology. This paper proposes a simulation-based approach to investigate the impact of various beamwidths on communication performance when using a buoy as a relay. The objective is to determine the optimal beamwidth that yields the highest data rate for the target location. The approach is based on an offshore wave model where the direction of the buoy changes according to the height of the wave. The study investigates the performance of the relay in the downlink situation using receive beamforming, and the capacity at the user in the three-hop situation is verified using an amplify-and-forward (AF) relay that uses transmit beamforming to the user. The simulation results suggest that the beamwidth of the relay should be adjusted according to the wave conditions to optimize the data rate and relay position that satisfies a data rate superior to the direct path to the target position. Using a buoy as a relay can be a promising solution for enhancing maritime communications, and the simulation-based approach proposed in this paper can provide insights into how to optimize beamwidth for effective communication system design and implementation. In conclusion, the study results suggest that the use of buoys as relays for maritime communication is a feasible solution for expanding coverage and enhancing communication quality. The proposed simulation-based approach provides a useful tool for identifying relay beamwidths for achieving higher data rates in different wave conditions. These findings have significant implications for the design and deployment of communication systems in maritime environments.
YOO, Hyun-Il,WOO, Kyung-Soo,PARK, Chang-Hwan,KIM, Jaekwon,JUNG, Sungyoon,CHO, Yong-Soo The Institute of Electronics, Information and Comm 2009 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.92 No.11
<P>In a Decode and Forward (DF) type of an OFDM-based Full Duplex Relay (FDR), the frequency-domain approach is more efficient than the time-domain approach for feedback interference cancellation. However, Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) may occur due to timing mismatch between the feedback interference signal and the desired signal from the Base Station (BS). In this letter, the effects of a timing mismatch on synchronous types and asynchronous types of OFDM-based FDRs are investigated in uplink and downlink cases. A synchronization procedure and techniques for minimizing ISI and ICI in OFDM-based FDRs with a frequency-domain feedback interference canceller are proposed.</P>