Catalytic Multilayers for Efficient Solar Water Oxidation through Catalyst Loading and Surface-State Passivation of BiVO₄ Photoanodes

Bae, Sanghyun,Kim, Hyunwoo,Jeon, Dasom,Ryu, Jungki American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.8

<P>We studied the kinetics of photoelectrochemical (PEC) water oxidation using a model photoanode BiVO<SUB>4</SUB> modified with various water oxidation catalysts (WOCs) by electrochemical impedance spectroscopy. In particular, we prepared BiVO<SUB>4</SUB> photoanodes with catalytic multilayers (CMs), where cationic polyelectrolytes and anionic polyoxometalate (POM) WOCs were assembled in a desired amount at a nanoscale precision, and compared their performance with those with well-known WOCs such as cobalt phosphate (CoPi) and NiOOH. Our comparative kinetics analysis suggested that the deposition of the CMs improved the kinetics of both the photogenerated charge carrier separation/transport in bulk BiVO<SUB>4</SUB> due to passivation of surface recombination centers and water oxidation at the electrode/electrolyte interface due to deposition of efficient molecular WOCs. On the contrary, the conventional WOCs were mostly effective in the former and less effective in the latter, which is consistent with previous reports. These findings explain why the CMs exhibit an outstanding performance. We also found that separated charge carriers can be efficiently transported to POM WOCs via a hopping mechanism due to the delicate architecture of the CMs, which is reminiscent of natural photosynthetic systems. We believe that this study can not only broaden our understanding on the underlying mechanism of PEC water oxidation but also provide insights for the design and fabrication of novel electrochemical and PEC devices, including efficient water oxidation photoanodes.</P> [FIG OMISSION]</BR>

Development of Creep and Mechanical Properties for SMAW Cr-Mo-X Steel Welds

Sanghyun Bae,Yongchul Kim,Stephen Liu 대한용접·접합학회 2024 대한용접·접합학회지 Vol.42 No.1

This research describes the development of new welding materials with high strength and high heat resistance for Cr-Mo-X type steels. Through thermodynamic simulation, the newly designed welding electrode had excellent mechanical properties, especially in high temperature tensile testing at 600℃ with 393.2 ㎫ tensile strength, 385.3 ㎫ yield strength and 23.5% elongation. Refinement of second phase particles were key to the success of the newly designed electrodes. Presence of M23C6 is noticeable in the new electrode welds which contributed to the high temperature strength and creep properties. Compared to conventional products, it was confirmed that the amount of M23C6 precipitates, measured in area fraction, increased substantially, from 5.9 to 11.9%. Z-phase, known to degrade weld mechanical properties, was reduced through adjusting chemical composition of the experimental welds. The reduction in Z-phase precipitates improved the brittle fracture resistance.

DB형 퇴직연금의 적립금운용계획서(IPS)에서 목표수익률 제약하의 자산배분전략

배상현 ( Sanghyun Bae ),정도영 ( Do Young Cheong ),강영선 ( Youngsun Kang ) 한국연금학회 2023 연금연구 Vol.13 No.2

2022년 근로자퇴직급여보장법이 개정됨에 따라, 300인 이상의 근로자를 상시 고용하는 DB형 퇴직연금을 도입한 기업은 적립금운용위원회를 의무적으로 개최하고 매년 1회 이상 적립금운용계획서(IPS; Investment Policy Statement)를 작성해야 한다. 본 연구에서는 시가총액 기준으로 국내 10대 기업을 선정하여 이들 기업의 평균적인 할인율 및 인금인상률을 목표수익률로 설정하고 자산배분안을 도출하는데 있어 재표본 효율모형(Resampled Efficiency)을 이용하였다. 분석결과 국내채권을 중심으로 해외주식 및 국내주식에 분산투자하는 자산배분안을 도출하였다. 롤링수익률 기반의 백테스팅을 통해 최적 자산배분안의 리스크를 살펴 본 결과, 5년 롤링수익률은 원금손실확률이 5%에서 통제되었으며, 10년 롤링수익률은 원금손실이 발생하지 않았다. 본 연구의 방법론과 결과는 적립금운용계획서 작성에 활용성이 높을 것으로 기대되며, 궁극적으로는 적정 적립비율 유지와 근로자의 수급권을 보호에도 기여할 것으로 기대된다. As the Employee Retirement Benefit Security Act is revised in 2022, companies that have introduced a DB-type retirement pension that employs 300 or more workers on a regular basis are required to hold a pension asset management committee and submit a investment policy statement at least once a year. In this study, we selected the top 10 domestic companies based on market capitalization, set the average discount rate and salary increase rate of these companies as the target rate of return, and derived an optimal asset allocation plan using the resampled efficiency model. As a result of the analysis, an optimal asset allocation plan was derived that diversifies investment in overseas and domestic stocks, focusing on domestic bonds. As a result of examining the risks of the optimal asset allocation plan through backtesting based on rolling returns, the probability of principal loss was controlled at 5% for the 5-year rolling return rate, and no principal loss occurred for the 10-year rolling return rate. The methodology and results of this study are expected to be highly useful in preparing a pension asset management plan, and are ultimately expected to contribute to maintaining an appropriate funded ratio and protecting workers' right to receive benefits.

진동형 에너지 하베스터의 비선형 공진 해석

배상현(Sanghyun Bae),김필기(Pilkee Kim),석종원(Jongwon Seok) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.4

류마티스관절염 환자의 불안, 우울, 자아존중감이 삶의 질에 미치는 영향

배상현(Bae, Sanghyun),홍인숙(Hong, Insook),조옥희(Cho, Ok-Hee) 기본간호학회 2021 기본간호학회지 Vol.28 No.2

Purpose: The purpose of this study was to investigate the influence and relationship among anxiety, depression, self-esteem, and quality of life, along with factors affecting quality of life, on patients with rheumatoid arthritis. Methods: This study was a cross-sectional descriptive study, and 200 individuals with rheumatoid arthritis who visited a single university hospital as outpatients were recruited through convenience sampling. Using a structured questionnaire, a survey was conducted regarding the general characteristics, anxiety, depression, self-esteem, and quality of life. Collected data were analyzed using t-test, ANOVA, and regression analysis. Results: Results showed that lower levels of anxiety or depression and higher levels of self-esteem were associated with improved quality of life. Depression was identified as the main factor affecting quality of life, followed by anxiety, glucocorticoid treatment, time elapsed after diagnosis, and occupational status. Conclusion: These findings confirmed that depression, anxiety, and glucocorticoid medication are factors influencing quality of life in patients with rheumatoid arthritis, Duration since diagnosis, and occupation should be considered in order to improve the quality of life of these patients with rheumatoid arthritis. The occupation and treatment-related characteristics of the patients must be considered, with particular focus on depression and anxiety.

A Study on Efficient Cluster Analysis of Bio-Data Using MapReduce Framework

Sowol Yoo, Kwangok Lee, Sanghyun Bae 조선대학교 기초과학연구원 2014 조선자연과학논문집 Vol.7 No.1

This study measured the stream data from the several sensors, and stores the database in MapReduce framework environment, and it aims to design system with the small performance and cluster analysis error rate through the KMSVM algorithm. Through the KM-SVM algorithm, the cluster analysis effective data was used for U-health system. In the results of experiment by using 2003 data sets obtained from 52 test subjects, the k-NN algorithm showed 79.29% cluster analysis accuracy, K-means algorithm showed 87.15 cluster analysis accuracy, and SVM algorithm showed 83.72%, KM-SVM showed 90.72%. As a result, the process speed and cluster analysis effective ratio of KM- SVM algorithm was better.

A Study on Emergency Monitoring Robot System by Back-Propagation Algorithm

Sowol Yoo, Miae Kim, Kwangok Lee, Sanghyun Bae 조선대학교 기초과학연구원 2014 조선자연과학논문집 Vol.7 No.1

This study aims to implement the emergency monitoring robot system which predicts the current state of the patients without visiting the medical institutions by measuring the basic health status of the user's blood pressure, heartbeat, and basic health status of body temperature in the disaster emergency situation based on the Smart Grid. By arranging a large number of sensor(blood pressure, heartbeat, body temperature sensor) and measuring the bio signs, so the attached wireless XBee sensor can be stored in DB of robot, and it aims to draw the current state of the patients by analysis of stored bio data. Among 300 data obtained from the sensor, 1st data to 100th data were used for learning, and from 101st data to 300th data were used for assessment. 12 results were different among the total 300 assessment data, so it shows about 96% accuracy.

Influence of Mg Flux on the Photoelectrochemical Properties of p-Type GaN for Hydrogen Production

Bae, Hyojung,Kim, Eunsook,Park, Jun-Beom,Fujii, Katsushi,Lee, Sanghyun,Lee, Hyo-Jong,Ryu, Sang-Wan,Lee, June Key,Ha, Jun-Seok American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.10

<P>This study investigates the effects of the doping flux of magnesium (Mg) on the photoelectrochemical (PEC) properties of p-type GaN. The Mg-doped GaN samples were deposited directly on c-plane Al2O3 substrates by metalorganic chemical vapor deposition (MOCVD). The Mg flux during growth was controlled by a mass flow controller at flows of 50, 100, 200, and 500 sccm. Optical property analysis revealed band-gaps for the films between 3.2 eV and 3.4 eV. The PEC properties of the films were examined by potentiostat with a three-electrode configuration. The photocurrent density of the 200 sccm sample was the highest, which would be attributed to vacancies or other intrinsic defects, such as interstitials and antisites, giving n-type conductivity.</P>

Intensity Histogram-Based Reliable Image Analysis Method for Bead-Based Fluorescence Immunoassay

Lee Sanghyun,Kim Juyeong,Bae Pan Kee,Lee Sangmin,김호진 한국바이오칩학회 2024 BioChip Journal Vol.18 No.1

Bead-based fluorescence immunoassay is drawing attention as a next-generation technology in disease diagnosis owing to its high sensitivity and multiplexing capability. Fluorescence imaging of beads is typically used to determine their mean fluorescence intensity. However, the mean intensity can be evaluated differently depending on the analysis methods [such as the shape and size of the region of interest (ROI)]. To address these problems, this study proposes a highly reliable and reproducible image analysis method utilizing a fluorescence intensity-based effective pixel extraction technique. Various potential sources of defective signals (e.g., fluorescence aggregation, non-specific antigen–antibody reactions, and bead defects) can be prevented from contributing to the average value by selectively extracting pixels representing the specific reactions of antigens and antibodies in the ROI. In this study, we fabricated a microfluidic chip composed of multiple bead- based detection lines, performed fluorescence immunoassay, and then compared the mean fluorescence intensity calculated from the fluorescence images with that of a conventional analysis method. Using the conventional method, the evaluated average mean intensity value of beads varied significantly based on the size of the ROI with the coeffi cients of variation ranging from approximately 29–95%. In contrast, the effective pixel extraction method resulted in a coefficient of variation of approximately 3–7% under varying ROI size. Furthermore, the coefficients of variation for four detection lines containing various types of defective signals signifi cantly decreased from approximately 7.1% to 2.6%. The proposed technique will help in minimizing the analysis deviation caused by different ROI selections or defective signals in fluorescent image-based immunoassays.

고점도 용액 정밀토출을 위한 노즐 직경 및 표면젖음성 특성 연구

이상현(Sanghyun Lee),배재현(Jae Hyeon Bae),이상민(Sangmin Lee) 한국기계가공학회 2021 한국기계가공학회지 Vol.20 No.12

Liquid dispensing systems are extensively used in various industries such as display, semiconductor, and battery manufacturing. Of the many types of dispensers, drop-on-demand piezoelectric jetting systems are widely used in semiconductor industries because of their ability to dispense minute volumes with high precision. However, due to the problems of nozzle clogging and undesirable dispensing behavior in these dispensers, which often result in device failure, the use of highly viscous fluids is limited. Accordingly, we studied the behaviors of droplet formation based on changes in viscosity. The effects of surface energy and the inner diameters of needle-type nozzles were also studied. Results showed that nozzles with lower surface energies reduced the ejection volume of droplets when a smaller nozzle diameter (0.21 mm in this study) was applied. These results indicate that the hydrophobic treatment of nozzle surfaces and the use of smaller nozzle diameters are critical factors enabling the use of highly viscous fluids in precision dispensing applications.