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Optimizing nanoparticle perovskite for bifunctional oxygen electrocatalysis
Jung, Jae-Il,Risch, Marcel,Park, Seungkyu,Kim, Min Gyu,Nam, Gyutae,Jeong, Hu-Young,Shao-Horn, Yang,Cho, Jaephil The Royal Society of Chemistry 2016 ENERGY AND ENVIRONMENTAL SCIENCE Vol.9 No.1
<P>Highly efficient bifunctional oxygen electrocatalysts are indispensable for the development of highly efficient regenerative fuel cells and rechargeable metal-air batteries, which could power future electric vehicles. Although perovskite oxides are known to have high intrinsic activity, large particle sizes rendered from traditional synthesis routes limit their practical use due to low mass activity. We report the synthesis of nano-sized perovskite particles with a nominal composition of La-x(Ba0.5Sr0.5)(1-x)Co0.8Fe0.2O3-delta (BSCF), where lanthanum concentration and calcination temperature were controlled to influence oxide defect chemistry and particle growth. This approach produced bifunctional perovskite electrocatalysts similar to 50 nm in size with supreme activity and stability for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The electrocatalysts preferentially reduced oxygen to water (o5% peroxide yield), exhibited more than 20 times higher gravimetric activity (A g(-1)) than IrO2 in OER half-cell tests (0.1 M KOH), and surpassed the charge/discharge performance of Pt/C (20 wt%) in zinc-air full cell tests (6 M KOH). Our work provides a general strategy for designing perovskite oxides as inexpensive, stable and highly active bifunctional electrocatalysts for future electrochemical energy storage and conversion devices.</P>
Hyperarousal-state of Insomnia Disorder in Wake-resting State Quantitative Electroencephalography
Gyutae Jang,Han Wool Jung,Jiheon Kim,Hansol Kim,Ji‑Hyeon Shin,Chan-Hyung Kim,Do-Hoon Kim,Sang-Kyu Lee,Daeyoung Roh 대한정신약물학회 2024 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.22 No.1
Objective: Insomnia is associated with elevated high-frequency electroencephalogram power in the waking state. Although affective symptoms (e.g., depression and anxiety) are commonly comorbid with insomnia, few reports distinguished objective sleep disturbance from affective symptoms. In this study, we investigated whether daytime electroencephalographic activity explains insomnia, even after controlling for the effects of affective symptoms. Methods: A total of 107 participants were divided into the insomnia disorder (n = 58) and healthy control (n = 49) groups using the Mini-International Neuropsychiatric Interview and diagnostic criteria for insomnia disorder. The participants underwent daytime resting-state electroencephalography sessions (64 channels, eye-closed). Results: The insomnia group showed higher levels of anxiety, depression, and insomnia than the healthy group, as well as increased beta [t (105) = −2.56, p = 0.012] and gamma [t (105) = −2.44, p = 0.016] spectra. Among all participants, insomnia symptoms positively correlated with the intensity of beta (r = 0.28, p < 0.01) and gamma (r = 0.25, p < 0.05) spectra. Through hierarchical multiple regression, the beta power showed the additional ability to predict insomnia symptoms beyond the effect of anxiety (ΔR2 = 0.041, p = 0.018). Conclusion: Our results showed a significant relationship between beta electroencephalographic activity and insomnia symptoms, after adjusting for other clinical correlates, and serve as further evidence for the hyperarousal theory of insomnia. Moreover, resting-state quantitative electroencephalography may be a supplementary tool to assess insomnia.
Influence of Surface Charges/Chemistry on the Catalysis of Perovskite Complexes
Park, Seungkyu,Nam, Gyutae,Lee, Jang-Soo,Cho, Jaephil,Jung, Jae-Il American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.34
<P>The electrochemical performance of the perovskite complex was discovered to depend greatly on the different locations of the identical particle, which represent different surface charges accordingly. The surface charges were evaluated by Zeta potential (ζ) for the intrinsic BSCF5582 (Ba<SUB>0.5</SUB>Sr<SUB>0.5</SUB>Co<SUB>0.8</SUB>Fe<SUB>0.2</SUB>O<SUB>3<I>-δ</I></SUB>), ball-milled (BM-BSCF5582), and heat-treated in an oxygen atmosphere after ball-milling (48h-O<SUB>2</SUB>-BM-BSCF5582), the mean ζ of which represents −11.1, 21.2, and −6.1 mV, respectively, which reflects well on different surface chemistries. When the bonding structures at the different stratified layers and the overall crystalline morphologies were analyzed via X-ray photoelectron spectroscopy and high resolution transmission electron microscopy, respectively, the crystalline- and bonding-structure at the 50 nm depth of BSCF5582 is nearly identical to that of BM-BSCF5582 at the surface. As ball-milling proceeds, not only are particles comminuted but also the amorphous surface is broken open, leading to the revelation of inner and naïve cubic crystalline phase surfaces and affecting the catalytic activities of oxygen evolution reactions and oxygen reduction reactions positively and negatively, respectively, at significant scales.</P> [FIG OMISSION]</BR>
Multi-Target Radar Tracking Estimation Algorithm for Automotive Embedded Applications
Minha Park,Seunghwan Seo,Gyutae Jung,Kukki Im 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
This paper presents tracking estimation algorithm and its feasibility analysis in computation load for the situation of multi-target automotive radar applications. Tracking algorithms have been evolved for many decades and played very important roles in space, military, and civilian sectors. Among many tracking methods, it is very critical task to utilize the most appropriate approach for each target application because there is always trade-off among performance, robustness, the computation load and etc. In the automotive world, unlike space and military industries, more constraints like cost and size should be taken into account in development within a certain limited time frame. Among them, the computation load is very significant in real-time embedded applications because the more computation capability is totally proportional to the cost increase of the system indeed. Based on literature researches and simulations, a couple of Kalman Filters were proposed as multi-target radar tracking estimation method and simulated and both elapsed time in simulation environments and in target board were compared and analyzed. As the system needs better performance and robustness in all situations, it will require more computation load in the processor resulting in the higher cost to the end. In the further research, the computation load should be analyzed in more details to adopt the most appropriate model for the specific application.
WBGT 27℃와 32℃의 고온 다습 환경에서 운동과 휴식 시 피부 수분도 및 생리적 주관적 발한 반응에서의 연령차
백윤정(Yoon Jeong Baek),배규태(Gyutae Bae),정다희(Dahee Jung),김규랑(Kyu Rang Kim),이주영(Joo-Young Lee) 한국생활환경학회 2019 한국생활환경학회지 Vol.26 No.4
The purpose of this study was to investigate physiological and subjective sweat responses of elderly and young males in hot and humid environments. Nine elderly and 11 young males participated in the following experimental conditions: WBGT 27℃ (Air temperature 30℃, and air humidity 70%RH) and WBGT 32℃ (35℃, 70%RH) with two activity levels (sitting on a chair for 60 min and walking on a treadmill for 60 min). The walking speeds were 4.0 km/hr for young males and 2.3 km/hr for elderly males. The results showed that 1) total sweating rate was 34.3% and 36.6% smaller for the elderly than for the young in WBGT 27℃ and 32℃, respectively (p<.05). Skin hydration at rest was less for the elderly than for the young in both WBGT 27℃ and 32-℃. The skin of the young males was quickly and evenly saturated throughout the whole body from the beginning in WBGT 32℃, whereas the elderly males’ skin was slowly and unevenly saturated. At rest, elderly males expressed greater humidity and sweat sensations in WBGT 27℃ than in WBGT 32℃ which was interpreted as perceptual confusions, while such perceptual confusions were not found during exercise in either WBGT 27℃ or WBGT 32℃. These results suggest that the elderly’s perspiration and other sweat responses in hot and humid environments were impaired psychologically as well as physiologically.
Spatial and Seasonal Variations of Ammonia in the Urban and Rural Environments in South Korea
Rahul Singh,Kyung Hoon Kim,Gyutae Park,Seokwon Kang,Taehyun Park,Ji Hee Ban,Si Young Choi,Jeong-in Song,Jung-Hun Woo,Taehyoung Lee 한국대기환경학회 2021 한국대기환경학회 학술대회논문집 Vol.2021 No.10
As an important environmental contaminant, atmospheric ammonia (NH₃) needs systematic measurement and assessment of emission generating factors all year long. A quantitative evaluation of the NH₃ concentration is conducted in several fields in South Korea. The Radiello Passive Sampler test techniques were utilized for evaluating the NH₃ data and validated with Denuder sampling of Annular (URG). In both urban and rural locations, testing is carried out to get a greater insight into the numerous components contributing to NH₃ pollution. The objective is to develop a standard experimental investigation of the fluctuations of the concentration through out the1-year period (2020-2021) by the implementation of the spatial and seasonal variations in the NH3 concentration. In all the locations that are taken into account, the fall season is reported to have the greatest NH₃ concentration in livestock and agricultural regions. Whereas the majority of the remaining testing locations showed the greatest rise in NH₃ concentration during the summer season and the least during the winter season. The purpose of this study was to find a relation between ammonia levels and temperature. The data analysis also helped to obtain a relation between ammonia concentration and height above landscape.
Yun, Jinyoung,Kim, Jaeyun,Jang, Ho-Kyun,Lee, Kook Jin,Seo, Jung Hwa,Jung, Byung Jun,Kim, Gyutae,Kwak, Jeonghun Elsevier 2017 ORGANIC ELECTRONICS Vol.50 No.-
<P><B>Abstract</B></P> <P>The balance of electron–hole charge carriers in quantum dot (QD) light-emitting diodes (QLEDs) is an important factor to achieve high efficiency. However, poor interfacial properties between QDs and their adjacent layers are likely to deteriorate the electron–hole charge balance, resulting in the poor performance of a QLED. In this paper, we report an enhanced efficiency in red-emitting inverted QLEDs by modifying the interface properties between QDs and ZnO electron transport layer (ETL) using a thin layer of non-conjugated polymer, poly(4-vinylpyridine) (PVPy). Based on the precise control of the electrical properties with PVPy, the maximum efficiency of the QLED is enhanced by 30% compared to the device without a PVPy layer. In particular, the efficiency at low current density region is significantly increased. We investigate the effect of the PVPy interlayer on the performance of QLEDs and find that this thin layer not only shifts the energy levels of the underlying ZnO ETL, but also effectively blocks the leakage current at the ETL/QD interface.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Tailored electron–hole balance using a PVPy interlayer improved QLED performance. </LI> <LI> PVPy interlayer efficiently blocked leakage current paths. </LI> <LI> PVPy interlayer reduced electron injection by shifting the energy levels of ZnO. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>