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Effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on tensile and bending properties of high-Al-containing Mg alloys

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Journal of Magnesium and Alloys 2024年第2期12卷 779-793页

作者： Sumi Jo Gyo Myeong lee jong Un lee Young Min Kim Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Department of Magnesium Korea Institute of Materials ScienceChangwon 51508Republic of Korea

This study investigates the effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on the uniaxial tensile and three-point bending properties of extruded Mg alloys containing high Al *** extruded Mg–9Al–1Zn–0.3Mn(AZ91)alloy contains lamellar-structured Mg_(17)Al_(12)discontinuous precipitates along the grain boundaries,which are formed via static precipitation during natural air *** extruded Mg–11Al–1Zn–0.3Mn(AZ111)alloy contains spherical Mg_(17)Al_(12)precipitates at the grain boundaries and inside the grains,which are formed via dynamic precipitation during *** to inhomogeneous distribution of precipitates,the AZ111 alloy consists of two different precipitate regions:precipitate-rich region with numerous precipitates and finer grains and precipitate-scarce region with a few precipitates and coarser *** AZ111 alloy exhibits a higher tensile strength than the AZ91 alloy because its smaller grain size and more abundant precipitates result in stronger grain-boundary hardening and precipitation hardening effects,***,the tensile elongation of the AZ111 alloy is lower than that of the AZ91 alloy because the weak cohesion between the dynamic precipitates and the matrix facilitates the crack initiation and *** bending,a macrocrack initiates on the outer surface of bending specimen in both *** AZ111 alloy exhibits higher bending yield strength and lower failure bending strain than the AZ91 *** bending specimens of the AZ91 alloy have similar bending formability,whereas those of the AZ111 alloy exhibit considerable differences in bending formability and crack propagation behavior,depending on the distribution and number density of precipitates in the *** bending specimens of the AZ111 alloy,it is found that the failure bending strain(ε_(f,bending))is inversely proportional to the area fraction of precipitates in the outer zone of bending specimen(A_(ppt)),with a relation

关键词： Mg–Al alloy Extrusion Bending Precipitation Microstructure

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Extended Kalman Filter-based localization algorithm by edge computing in Wireless Sensor Networks

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Digital Communications and Networks 2021年第2期7卷 187-195页

作者： Inam Ullah Siyu Qian Zhixiang Deng jong-Hyouk lee College of Internet of Things(IoT)Engineering Hohai UniversityChangzhou Campus213022China Department of Computer and Information Security Sejong UniversitySeoul05006Republic of Korea

The Extended Kalman Filter(EKF)has received abundant attention with the growing demands for robotic *** EKF algorithm is more realistic in non-linear systems,which has an autonomous white noise in both the system and the estimation ***,in the field of engineering,most systems are ***,the EKF attracts more attention than the Kalman Filter(KF).In this paper,we propose an EKF-based localization algorithm by edge computing,and a mobile robot is used to update its location concerning the *** localization algorithm aims to achieve a high level of accuracy and wider *** proposed algorithm is helpful for the research related to the use of EKF localization *** results demonstrate that,under the situations presented in the paper,the proposed localization algorithm is more accurate compared with the current state-of-the-art localization algorithms.

关键词： Extended Kalman filter Edge computing Kalman filter Localization Robots State estimation

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Novel Intense-pulsed-light synthesis of amorphous SnO_(2)electron-selective layers for efficient planar MAPbI_(3)perovskite solar cells

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Journal of Materials Science & Technology 2021年第33期92卷 171-177页

作者： Kwonwoo Oh Kyungeun Jung Jaehak Shin Sunglim Ko Man-jong lee Department of Chemistry Konkuk UniversitySeoul 143-701Republic of Korea Department of Advanced Technology Fusion Konkuk UniversitySeoul 143-701Republic of Korea Department of Mechanical Design and Production Engineering Konkuk UniversitySeoul 143-701Republic of Korea

Although perovskite solar cells(PSCs)have achieved a high power conversion efficiency(PCE)within a short period of development,the high-temperature sintering of the constituent electron-selective layers(ESLs)impedes the *** this report,we demonstrate the effectiveness of an intensepulsed-light(IPL)treatment for the rapid and damage-free sintering of amorphous-SnO_(2)ESLs for use in *** IPL treatment of amorphous-SnO_(2)substantially reduced the amount of surface hydroxyl groups,modified the surface energy,and enabled the growth of a low-stress perovskite layer with large grain sizes,all of which enhanced the photovoltaic properties and led to the proper alignment of band structures for efficient *** comprehensive optimization of the IPL conditions,a PCE of 17.68%was achieved from the MAPb I3 planar PSC based on an amorphous-SnO_(2)IPL treated for a few tens of seconds,which was significantly increased compared with a PCE(7.06%)of nontreated SnO_(2)based *** addition,the PCE of the IPL-treated SnO_(2)based PSC is comparable to the best PCE(18.16%)of PSCs fabricated with SnO_(2)ESL annealed for three hours at 185℃.Because of its ultrafast sintering time and tendency to not damage SnO_(2)ESLs,the new IPL process is expected to open new opportunities for the commercialization of PSCs.

关键词： Perovskite solar cells Intense pulsed light Amorphous SnO_(2) Electron-selective layer Internal stress

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Solar-harvesting lead halide perovskite for artificial photosynthesis

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Journal of Energy Chemistry 2021年第11期30卷 11-26,I0001页

作者： Sunje lee Gyu Yong Jang Jung Kyu Kim jong Hyeok Park Department of Chemical and Biomolecular Engineering Yonsei University50 Yonsei-roSeodaemun-guSeoul 03722Republic of Korea School of Chemical Engineering Sungkyunkwan University(SKKU)2066 Seobu‐roJangan‐guSuwon 16419Republic of Korea

Facing the upcoming energy and environmental crisis, artificial photosynthesis for producing various solar fuels (e.g., hydrogen or carbon products) via a solar-to-chemical energy conversion is receiving increasing attention;however, its low conversion efficiency is a challenge for commercialization. To resolve low-efficiency issues, lead halide perovskite (LHP) with outstanding optoelectronic properties compared to conventional semiconductors can be a promising approach to improve the solar-to-fuel conversion reactions and solar fuel production efficiency. The tunable energy band structure and charge transport properties of LHP have promoted their extensive use in the production of solar fuels. This study summarizes the recent advancements of LHP-mediated solar-to-fuel conversions, classified by their redox reactions, namely solar water splitting, hydrohalic acid splitting, and CO_(2) reduction. Advanced approaches for achieving high conversion efficiency and long-term durability are discussed, including the configuration of devices, the composition of LHP, and the protection strategy of LHP. Moreover, the reaction mechanisms of LHP-mediated solar-to-chemical energy conversions and obstacles for enhancing the conversion efficiency are discussed. Finally, we present the perspectives on the development of LHP-incorporated solar-to-fuel conversion systems, which might open a new era of energy harvesting and storage.

关键词： Perovskite Photocatalytic reaction Photoelectrochemistry Photovoltaic Water splitting HI splitting CO_(2)reduction

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Newly diagnosed diabetes mellitus patients presenting with proliferative diabetic retinopathy as an initial sign

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International Journal of Ophthalmology(English edition) 2014年第1期7卷 173-178页

作者： Hoon Park Young Gyun Kim jong Wook lee jong Seok Park Department of Ophthalmology Eulji Hospital

AIM: To investigate the clinical features of newly diagnosed diabetes mellitus(NDM) patients showing proliferative diabetic retinopathy(PDR) as an initial sign. ·METHODS: As a retrospective case series,the medical records of a total of four hundred and thirty-two patients who underwent a vitrectomy due to PDR were reviewed to find the subjects. Of 432 patients,six cases of NDM patients showing PDR as an initial sign were included and analyzed with their systemic and ocular features. Main outcome measures: the systemic features and ocular features [preoperative and postoperative best corrected visual acuity(BCVA),intraoperative findings]. ·RESULTS: The mean onset age of visual symptoms was 36.3 years old. The mean serum insulin and C-peptide titer was below the normal range. The mean fasting plasma glucose was 178mg/dL and the mean postprandial 2h plasma glucose was 306mg/dL. The mean HbA1c at diagnosis was 11.02%. In all cases,an acute progressive fibrovascular proliferation was observed. Intraoperative retinal tears were found in three cases of six. The mean preoperative BCVA was +0.67 ± 0.58 logMAR and the mean BCVA at postoperative 6 months was +0.20±0.30 logMAR. ·CONCLUSION: All patients were considered to have latent autoimmune diabetes in adults(LADA). A rapid deterioration of kidney function as well as poor diabetic control status at diagnosis was observed in all six cases. The ocular features of the patients showed acute progressive fibrovascular proliferation and relatively favorable postoperative visual acuity.

关键词： fibrovascular proliferation latent autoimmune diabetes in adults diabetes mellitus proliferative diabetic retinopathy

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Precise control of surface oxygen vacancies in ZnO nanoparticles for extremely high acetone sensing response

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Journal of Advanced Ceramics 2022年第5期11卷 769-783页

作者： Jihyun lee Youngmoon CHOI Byoung Joon PARK Jeong Woo HAN Hyun-Sook lee jong Hyeok PARK Wooyoung lee Department of Materials Science and Engineering Yonsei UniversitySeoul 03722Republic of Korea Department of Chemical and Biological Engineering Yonsei UniversitySeoul 03722Republic of Korea Department of Chemical Engineering Pohang University of Science and TechnologyPohang 37673Republic of Korea Institute for Convergence Research and Education in Advanced Technology Yonsei UniversitySeoul 03722Republic of Korea

ZnO has been studied intensely for chemical sensors due to its high sensitivity and fast ***,we present a simple approach to precisely control oxygen vacancy contents to provide significantly enhanced acetone sensing performance of commercial ZnO nanopowders.A combination of H_(2)O_(2)treatment and thermal annealing produces optimal surface defects with oxygen vacancies on the ZnO nanoparticles(NPs).The highest response of~27,562 was achieved for 10 ppm acetone in 0.125 MH_(2)O_(2)treated/annealed ZnO NPs at the optimal working temperature of 400℃,which is significantly higher than that of reported so far in various acetone sensors based on metal oxide semiconductors(MOSs).Furthermore,first-principles calculations indicate that pre-adsorbed O formed on the surface of H_(2)O_(2)treated ZnO NPs can provide favorable adsorption energy,especially for acetone detection,due to strong bidentate bonding between carbonyl C atom of acetone molecules and pre-adsorbed O on the ZnO *** study demonstrates that controlling surface oxygen vacancies by H_(2)O_(2)treatment and re-annealing at optimal temperature is an effective method to improve the sensing properties of commercial MOS materials.

关键词： gas sensors acetone metal oxide semiconductors(MOSs) ZnO nanoparticles(NPs) H_(2)O_(2)treatment

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Effect of esterification reaction of citric acid and ethylene glycol on the formation of multi-shelled cobalt oxide powders with superior electrochemical properties

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Nano Research 2014年第12期7卷 1738-1748页

作者： Gi Dae Park jong-Heun lee Jung-Kul lee Yun Chan Kang Department of Materials Science and Engineering Korea University Anam-Dong Seongbuk-Gu Seou1136-713 Republic of Korea Department of Chemical Engineering Konkuk University 1 Hwayang-dong Gwangjin-gu Seou1143-701 Republic of Korea

In this study, for the first time, polymeric precursors have been used in the preparation of yolk-shell powders using a large-scale spray drying process. An esterification reaction between the carboxyl group of citric acid and the hydroxyl group of ethylene glycol inside the droplet produced organic polymers during the drying process of the droplet. During the spray drying process, the polymeric precursors enabled the formation of multi-shell cobalt oxide yolk- shell powders with superior electrochemical properties. The maximum number of shells of the particles in the yolk-shell powders post-treated at 300, 400, and 500 ℃ were six, five, and four, respectively. The initial discharge capacities of the cobalt oxide yolk-shell powders post-treated at 300, 400, and 500 ℃ were 1,188, 1,331, and 1,110 mAh·g^-1, and their initial charge capacities were 868, 1,005, and 798 mAh·g^-1, respectively. The discharge capacities of the powders post- treated at 300, 400, and 500 ℃ after 100 cycles were 815, 958, and 670 mAh·g^-1, respectively and their corresponding capacity retentions measured after the first cycles were 92%, 93%, and 82%, respectively. The pure phase Co3O4 yolk-shell powders post-treated at 400 ℃ had low charge transfer resistance and high lithium-ion diffusion rate.

关键词： yolk-shell energy storage synthesis design lithium battery spray drying

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Agmatine reduces nitric oxide synthase expression and peroxynitrite formation in the cerebral cortex in a rat model of transient global cerebral ischemia

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Neural Regeneration Research 2010年第23期5卷 1773-1781页

作者： Chin Hee Mun Won Taek lee Kyung Ah Park jong Eun lee Department of Anatomy Yonsei University College of Medicine Brain Korea 21 Project for Medical Science Yonsei University College of Medicine

Agmatine, an analog of L-arginine, is an endogenous substance synthesized by arginine decarboxylase, which has been shown to possess neuroprotective effects following brain ischemia. Nitric oxide is generated by sequential oxidation of the guanidinium group in L-arginine, and agmatine might protect the brain from ischemic injury by interfering with nitric oxide signaling. This study investigated the effects of agmatine on cerebral cortex neuronal injury following transient global cerebral ischemia and also detected nitric oxide synthase expression and peroxynitrite formation. Results demonstrated that intraperitoneal injection of agmatine in global cerebral ischemia/reperfusion alleviated ischemia/reperfusion-induced cerebral cortical cortex neuronal injury and cellular apoptosis, decreased neuronal and inducible nitric oxide synthase expression at 24, 48, and 72 hours following global cerebral ischemia and reperfusion, and greatly inhibited nitrotyrosine levels, which reflect the amount of peroxynitrite formed. These findings indicated that agmatine alleviates cerebral cortex neuronal injury following global cerebral ischemia and decreases nitric oxide synthase expression and peroxynitrite formation following ischemia/repeffusion.

关键词： agmatine global cerebral ischemia cerebral cortex nitric oxide nitric oxide synthase neuroprotection

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Collapse behavior evaluation of hybrid thin-walled member by stacking condition

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Transactions of Nonferrous Metals Society of China 2011年第A1期21卷 135-140页

作者： kil-Sung lee Hyeon-Kyeong SEO Yong-June YANG Woo-Chae HWANG Kwang-Hee IM In-Young YANG R&D Center Dacc LTD. 948-13 Dunsan-ri Bongdong-eup Wanju-gun Jeonbuk 565-902 Korea Departments of Advanced Parts and Materials Engineering Graduate School Chosun University Department of Automotive Engineering Woosuk University Departments of Mechanical Design Engineering Chosun University

The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, the energy absorbing members should absorb collision energy sufficiently but for the environmentally-friendly aspect, the vehicle structure must be light weight in order to improve the fuel efficiency and reduce the tail gas emission. Therefore, the light weight of vehicle must be achieved in a securing safety status of crash. An aluminum or carbon fiber reinforced plastics (CFRP) is representative one of the light-weight materials. Based on the respective collapse behavior of aluminum and CFRP member, the collapse behavior of hybrid thin-walled member was evaluated. The hybrid members were manufactured by wrapping CFRP prepreg sheets outside the aluminum hollow members in the autoclave. Because the CFRP is an anisotropic material whose mechanical properties, such as strength and elasticity, change with its stacking condition, the effects of the stacking condition on the collapse behavior evaluation of the hybrid thin-walled member were tested. The collapse mode and energy absorption capability of the hybrid thin-walled member were analyzed with the change of the fiber orientation angle and interface number.

关键词： collapse behavior aluminum and CFRP hybrid thin-walled member stacking condition

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Spectroscopic Understanding of Structural and Electrical Property Variations in Dopant-Free ZnO Films

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Journal of Materials Science & Technology 2017年第6期33卷 523-526页

作者： Hyegyeong Kim JiWoong Kim Dooyong lee Won-Jae lee jong-Seong Bae Jaekwang lee Sungkyun Park Department of Physics Pusan National University Department of Nano Engineering & Electronic Research Center Dong-Eui University Busan Center Korea Basic Science Institute

Physical property variation in dopant-free ZnO films was investigated. Film annealing under various environments（O_2, in-Air, N2 and vacuum） resulted in better crystallinity than in the as-grown film. In particular, the film annealed under the N_2 environment showed better crystallinity and electrical properties than films annealed in other environments. Based on spectroscopic analysis, we found a correlation between physical（structural, electrical） and chemical properties： The crystallinity of ZnO films is closely related to ZnO bonding, whereas carrier concentration is associated with VO（oxygen vacancy）.

关键词： ZnO films Annealing Oxygen vacancies Environmental stability

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