Elongated Lifetime and Enhanced Flux of Hot Electrons on a Perovskite Plasmonic Nanodiode

Park, Yujin,Choi, Jungkweon,Lee, Changhwan,Cho, An-Na,Cho, Dae Won,Park, Nam-Gyu,Ihee, Hyotcherl,Park, Jeong Young American Chemical Society 2019 NANO LETTERS Vol.19 No.8

<P>A fundamental understanding of hot electron transport is critical for developing efficient hot-carrier-based solar cells. There have been significant efforts to enhance hot electron flux, and it has been found that a key factor affecting the hot electron flux is the lifetime of the hot electrons. Here, we report a combined study of hot electron flux and the lifetime of hot carriers using a perovskite-modified plasmonic nanodiode. We found that perovskite deposition on a plasmonic nanodiode can considerably improve hot electron generation induced by photon absorption. The perovskite plasmonic nanodiode consists of MAPbI<SUB>3</SUB> layers covering a plasmonic-Au/TiO<SUB>2</SUB> Schottky junction that is composed of randomly connected Au nanoislands deposited on a TiO<SUB>2</SUB> layer. The measured incident photon-to-electron conversion efficiency and the short-circuit photocurrent show a significantly improved solar-to-electrical conversion performance of this nanodiode. Such an improvement is ascribed to the improved hot electron flux in MAPbI<SUB>3</SUB> caused by effective light absorption from near-field enhancement of plasmonic Au and the efficient capture of hot electrons from Au nanoislands via the formation of a three-dimensional Schottky interface. The relation between the lifetime and flux of hot electrons was confirmed by femtosecond transient absorption spectroscopy that showed considerably longer hot electron lifetimes in MAPbI<SUB>3</SUB> combined with the plasmonic Au structure. These findings can provide a fundamental understanding of hot electron generation and transport in perovskite, which can provide helpful guidance to designing efficient hot carrier photovoltaics.</P> [FIG OMISSION]</BR>

Association between Type and Intensity of Physical Activity and Depression

Yujin Chang,Kye-Yeung Park,Hwan-Sik Hwang,Hoon-Ki Park 대한가정의학회 2022 Korean Journal of Family Medicine Vol.43 No.4

Background: Although numerous studies have indicated that lower levels of physical activity correlate with a high-er risk of depression, an association between the type of physical activity and depression has not been identified in Korea. This study aimed to examine whether the type and intensity of physical activity are associated with depres-sion in Korean adults.Methods: This cross-sectional study used data from the Korea National Health and Nutrition Examination Survey (KNHANES). A total of 11,679 individuals were analyzed using multiple logistic regression analyses to identify any association between the type of physical activity and depressive disorders in the sample subjects.Results: Measured weekly in units of energy expenditure, known as metabolic equivalents (METs), the amount of work-related physical activity was higher in individuals with depression according to the Patient Health Question-naire-9 than the participants without depression (386.7 vs. 206.7 MET-min/wk, P=0.01). Those diagnosed with de-pression tended to engage in less recreational activity per week (143.7 vs. 316.3 MET-min/wk, P<0.001) than those without depression. After controlling for covariates, the risk of depression among all participants was 1.012 times higher with a 100-unit increase in total work-related activity measured in METs (95% confidence interval [CI], 1.006–1.017; P<0.001) and 0.962 times lower with a 100-unit increase in total leisure activity measured in METs (95% CI, 0.937–0.987; P=0.003).Conclusion: Different types of physical activity were shown to be differently associated with depressive disorders in Korean adults. This study might guide in reducing work-related physical activity and increasing leisure activity to prevent the occurrence of depression.

Locking-In Optimal Nanoscale Structure Induced by Naphthalenediimide-Based Polymeric Additive Enables Efficient and Stable Inverted Polymer Solar Cells

Park, Kwang Hyun,An, Yujin,Jung, Seungon,Park, Hyesung,Yang, Changduk American Chemical Society 2017 ACS NANO Vol.11 No.7

<P>Operational stability and high performance are the most critical issues that must be addressed in order to propel and advance the current polymer solar cell (PSC) technology to the next level, such as manufacturing and mass production. Herein, we report a high power conversion efficiency (PCE) of 11.2%, together with an excellent device stability in PTB7-Th:PC71BM-based PSCs in the inverted structure by introducing the n-type P(NDI2OD-T2) macromolecular additive (>75% PCE retention at high temperature up to 120 degrees C, >97% PCE retention after 6 months in inert conditions, >93% PCE retention after 2 months in air with encapsulation, and >80% PCE retention after 140 h in air without encapsulation). The PCE is the highest value ever reported in the single-junction systems based on the PTB7 family and is also comparable to the previously reported highest PCE of inverted PSCs. These promising results are attributed to the efficient optimization and stabilization of the blend film morphology in the photoactive layer, achieved using the P(NDI2OD-T2) additive. From the perspective of manufacturing, our studies demonstrate a promising pathway for fabricating low-cost PSCs with high efficiency as well as long-term stability.</P>

Effects of the different dietary feed additives on growth performance and non-specific immune responses of juvenile Olive flounder, Paralichthys olivaceus

Yujin Song,Jinhyuck Lee,Haham Kim,Minhye Park,Gunhyun Park,Sungchul C. Bai 한국수산과학회 양식분과 2017 한국수산과학회 양식분과 학술대회 Vol.2017 No.5

Insomnia in North Korean Refugees: Association with Depression and Post-Traumatic Stress Symptoms

YuJin G. Lee,JinYong Jun,YuJin Lee,Juhyun Park,Soohyun Kim,SoHee Lee,SoYoung Yu,SeogJu Kim 대한신경정신의학회 2016 PSYCHIATRY INVESTIGATION Vol.13 No.1

Objective-We investigated the prevalence of insomnia and its clinical characteristics in North Korean refugees. Methods-North Korean refugees living in South Korea (48 males, 129 females; mean age 38.22±12.24 years) and South Koreans (112 males, 203 females; mean age 39.48±10.32 years) completed the following questionnaires: the Self-reported Questionnaire on Insomnia, Center for Epidemiological Studies-Depression Scale (CES-D), Trauma Exposure Check List for North Korean Refugees, and the Impact of Event Scale-Revised (IES-R). Results-North Korean refugees had insomnia more often than South Koreans did (38.42% vs. 8.89%). Depression combined with insomnia was also more prevalent in North Korean refugees (28.25% vs. 3.17%). Compared with South Koreans with insomnia, North Korean refugees with insomnia showed higher CES-D scores. The North Korean refugees with insomnia had experienced a larger number of traumatic events, and had higher CES-D and IES-R scores compared to North Korean refugees without insomnia. Insomnia in North Korean refugees was also associated with the presence of significant depressive and post-traumatic stress disorder (PTSD) symptoms. Conclusion-Insomnia was common in North Korean refugees and was closely associated with depressive and PTSD symptoms. Our study suggests that complaints of insomnia may indicate more severe psychopathology, especially in refugees.

Utilization of turanose as a quality improver in gluten-free extruded rice noodles

Yujin Park,Sang-Ho Yoo,Sung Won Park,Suyong Lee 한국산업식품공학회 2017 학술대회 및 심포지엄 Vol.2017 No.11

Gluten-free industry has experienced consistent growth with increasing the number of individuals with celiac disease. Among gluten-free products, the popularity of rice noodles has been worldwide increasing over the recent years. However, rice noodles have several processing limitations such as high cooking turbidity and long cooking time. Therefore, various ingredients have been incorporated into the formulation of rice noodles in order to improve their quality attributes. In this study, turanose which is known to be a new sugar alternative with low sweetness was applied to rice noodles and their effects were characterized in terms of thermal, rheological, and textural properties. Gluten-free rice noodles were prepared with different levels of turanose (0.5, 1.0, 1.5%, w/w) by using a twin-screw extruder. Rice flour with turanose had higher gelatinization temperature and also showed higher enthalpy values after storage at 4°C. The use of turanose also increased the pasting and mixing parameters of rice flour. In addition, the application of turanose to rice noodles affected their qualities such as texture and cooking loss. Thus, this study demonstrated that turanose could positively contribute to enhancing the qualities of gluten-free rice noodles as a new additive.

Protein Detection Based on The Target-induced DNA Polymerase Activity Modulation

Yujin JUNG,Chang Yeol LEE,Ki Soo PARK,Hyun Gyu PARK 한국생물공학회 2018 한국생물공학회 학술대회 Vol.2018 No.4

Evaluating the effects of organic matter bioavailability on nanofiltration membrane using real-time monitoring

Park, Sanghun,You, Jeongyeop,Ahn, Yujin,Jung, Woonggyu,Kim, Jihye,Lee, Sungyun,Park, Jongkwan,Cho, Kyung Hwa Elsevier 2018 Journal of membrane science Vol.548 No.-

<P><B>Abstract</B></P> <P>We studied the influence of bioavailability of organic matter on membrane fouling layer development by comparing the filtration performance of two feed waters (wetland water and graywater). Dissolved organic carbon (DOC) concentration, size exclusion chromatography (SEC), and fluorescence excitation-emission matrix (FEEM) were used to characterize the bioavailability of organic matter in these water samples during the nanofiltration process. The wetland sample contained a high proportion of humic acid- and fulvic acid-like matter with low bioavailability, whereas the graywater sample comprised substantial amounts of aromatic proteins and microbial byproduct-like matter with high bioavailability. In addition, the molecular size distribution revealed that the wetland sample contained a large portion of recalcitrant organic matter, whereas the graywater sample contained easily bioavailable organic matter. After the filtration experiment, the DOC of the wetland sample decreased to 4.8mgC/L, whereas the graywater sample resulted in a lower DOC concentration of 3.4mgC/L. Optical coherence tomography (OCT) illustrated real-time variations in the fouling layer morphology, providing both 2D and 3D images. In addition, confocal laser scanning microscopy (CLSM) quantified the bacterial volume in the fouling layer. The wetland sample yielded a bacterial volume of 11.8µm<SUP>3</SUP>/μm<SUP>2</SUP> from a total fouling volume of 103µm<SUP>3</SUP>/μm<SUP>2</SUP>, whereas the graywater sample yielded a bacterial volume of 53.2µm<SUP>3</SUP>/μm<SUP>2</SUP> from a total fouling layer volume of 134µm<SUP>3</SUP>/μm<SUP>2</SUP>. Fitting of the two-phase Monod model to the fouling layer growth on the membrane resulted in lower-yield coefficients (i.e., the volumes produced per unit amount of substrate, <SUB> Y xs </SUB> ) of 7.46 and 27.95µm<SUP>3</SUP>/μm<SUP>2</SUP> in wetland water and higher-yield coefficients of 13.17 and 47.53µm<SUP>3</SUP>/μm<SUP>2</SUP> in the graywater at first and second phase, respectively. This study addresses the quantitative evaluation of the organic matter bioavailability in terms of membrane fouling using OCT images and a two-phase Monod model.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The difference of bioavailability of DOM influenced the amount of fouling layer growth. </LI> <LI> In situ OCT monitoring provided 2D and 3D morphology of the fouling layer and quantified the volume. </LI> <LI> Two-phase Monod model evaluated the influence of bioavailability of DOM on fouling layer growth. </LI> </UL> </P>

Microwave-assisted Synthesis of Fluorescent Polymer Dots from Hyperbranched Polyethylenimine and Glycerol

Park, Jongyeap,Kwon, Binhee,Jeong, Woojun,Chae, Ari,Choi, Yujin,Park, Sung Young,In, Insik Chemical Society of Japan 2017 Chemistry letters Vol.46 No.10

Exploring Online Learning Profiles of In-service Teachers in a Professional Development Course

( Yujin Park ),( Jihyun Sung ),( Young Hoan Cho ) 한국교육공학회 2017 Educational Technology International Vol.18 No.2

This study aimed to explore online learning profiles of in-service teachers in South Korea, focusing on video lecture and discussion activities. A total of 269 teachers took an online professional development course for 14 days, using an online learning platform from which web log data were collected. The data showed the frequency of participation and the initial participation time, which was closely related to procrastinating behaviors. A cluster analysis revealed three online learning profiles of in-service teachers: procrastinating (n=42), passive interaction (n=136), and active learning (n=91) clusters. The active learning cluster showed high-level participation in both video lecture and discussion activities from the beginning of the online course, whereas the procrastinating cluster was seldom engaged in learning activities for the first half of the learning period. The passive interaction cluster was actively engaged in watching video lectures from the beginning of the online course but passively participated in discussion activities. As a result, the active learning cluster outperformed the passive interaction cluster in learning achievements. The findings were discussed in regard to how to improve online learning environments through considering online learning profiles of in-service teachers.