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Fracture Characteristics of Frit Bonding through In-Situ Nano-Indentation Testing

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journal of Materials Science & Technology 2016年第11期32卷 1204-1210页

作者： Won Je jo Hee-Jun Ahn jong Hyoung kim Dongil Kwon Department of Materials Science and Engineering Seoul National University

Because frit bonding material is brittle, sudden impacts such as dropping may damage the bonding significantly. Strain-rate-controlled in-situ nano-indentation testing, which can determine localized material properties, was carried out on the frit-bonded specimen, especially on the frit bonding matrix and the filler. The results were compared with the drop-impact fracture behavior to understand the fracture characteristics. Mechanical properties at static condition or low strain rate did not show proper relationship with the fracture tendency of the drop tested result of the frit bonding. From the relationship between fracture toughness and the ratio of modulus/hardness, fracture characteristics at the drop impact situation could be estimated by the values at the high strain rate nano-indentation. The ratio between modulus and hardness on frit matrix showed close relationship with drop impact fracture. Though crack propagation path deflected at filler interface, filler property gave less influence on fracture tendency of drop impact fracture due to its small volume fraction. The properties of frit matrix were crucial to the fracture characteristics of the frit bonding.

关键词： Nanoindentation Bonding Fracture behavior

Effects of Cu addition on formability and surface delamination phenomenon in high-strength high-Mn steels

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journal of Materials Science & Technology 2020年第8期36卷 44-51页

作者： Min Chul jo Jisung Yoo Min Cheol jo Alireza Zargaran Seok Su Sohn Nack J.kim Sunghak Lee Center for Advanced Aerospace Materials Pohang University of Science and TechnologyPohang 37673South Korea Graduate Institute of Ferrous Technology Pohang University of Science and TechnologyPohang 37673South Korea Department of Materials Science and Engineering Korea UniversitySeoul 02841South Korea

The formability of austenitic high-Mn steels is a critical issue in automotive applications under nonuniformly-deformed environments caused by dynamic strain *** austenite stabilizing alloying elements in those steels,Cu has been known as an effective element to enhance tensile properties via controlling the stacking fault energy and stability of *** effects of Cu addition on formability,however,have not been sufficiently reported *** this study,the Cu addition effects on formability and surface characteristics in the austenitic high-Mn TRIP steels were analyzed in consideration of inhomogeneous microstructures containing the segregation of Mn and *** reveal determining factors,various mechanical parameters such as total elongation,post elongation,strain hardening rate,normal anisotropy,and planar anisotropy were correlated to the hole-expansion and cup-drawing test *** respect to microstructural parameters,roles of(Mn,Cu)-segregation bands and resultant Cu-rich FCC precipitates on the formability and surface delamination were also discussed.

关键词： High-Mn steel Cu effects Cu-rich FCC phase Hole-expansion test Formability Stretch-flangeablity Surface delamination

Heterojunction between bimetallic metal-organic framework and TiO_(2):Band-structure engineering for effective photoelectrochemical water splitting

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Nano Research 2022年第9期15卷 8502-8509页

作者： Ji Won Yoon Jae-Hyeok kim Young-Moo jo jong-Heun Lee Department of Materials Science and Engineering Korea UniversitySeoul 02841Republic of Korea

Bimetallic Fe/Ni-based metal-organic frameworks(MOFs)with different Fe/Ni ratios were coated on TiO_(2)nanorods(NRs),and the performances of the heterojunction photoanodes in photoelectrochemical water splitting were *** bandgaps and band positions of the MOFs could be modulated by changing the ratio of the Fe and Ni *** ideal band alignment was achieved between the TiO_(2)NRs and bimetallic MOFs with an optimum ratio of[Fe]/[Ni]=0.25/0.75,which allowed efficient light absorption and charge *** coating of NH_(2)-MIL(Fe)-88 layer on the TiO_(2)NRs decreased the photocurrent density by 33%.In comparison,TiO_(2)/NH_(2)-MIL(Ni)-88 showed a modest improvement in photocurrent density(0.85 mA·cm^(−2)at 1.23 V vs.a reversible hydrogen electrode(RHE)).When bimetallic NH_(2)-MIL(Fe_(0.25)Ni_(0.75))-88 was coated on the TiO_(2)NRs,the photocurrent density reached 1.56 mA·cm^(−2),which was an efficiency enhancement of 3.2 *** mechanism underlying high photoelectrochemical performance was investigated.

关键词： band-structure engineering bimetallic metal-organic frameworks(MOFs) solar water splitting TiO_(2)nanorods NH_(2)-MIL-88

Fabrication of perovskite solar cell with high short-circuit current density(Jsc)using moth-eye structure of SiOx

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Nano Research 2020年第4期13卷 1156-1161页

作者： Sucheol Ju Minseop Byun Minjin kim Junho Jun Daihong Huh Dong Suk kim Yimhyun jo Heon Lee Department of Materials Science and Engineering Korea UniversityAnam-ro 145Sungbuk-GuSeoul 136-701Republic of Korea KIER-UNIST Advanced Center for Energy Korea Institute of Energy Research(KIER)UNIST-Gil 50Eonyang-eupUlju-gunUlsan 689-851Republic of Korea

The performance of solar cells is determined by three factors:the open-circuit voltage(Voc),short-circuit current density(Jsc),and fill factor(FF).The Voc and FF are determined by the material bandgap and the series/shunt resistance,***,Jsc is determined by the amount of incident light in addition to the bandgap of the *** this study,a moth-eye pattern was formed on a glass surface via direct printing to increase the amount of incident light and thus increase Jsc-The moth-eye pattern is a typical antireflection pattern that reduces the reflection by gradually increasing the refractive index.A flat perovskite solar cell(F-PSC)and a moth-eye patterned perovskite solar cell(M-PSC)had Jsc values of 23.70 and 25.50 mA/cm^2,*** power-conversion efficiencies of the F-PSC and M-PSC were 19.81%and 21.77%,respectively.

关键词： perovskite solar cells direct printing moth-eye pattern hydrogen silsesquioxane

Metal organic framework-combustion: A one-pot strategy to NiO nanoparticles with excellent anode properties for lithium ion batteries

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journal of Energy Chemistry 2018年第1期27卷 300-305页

作者： Vaiyapuri Soundharrajan Balaji Sambandam Jinju Song Sungjin kim Jeonggeun jo Pham Tung Duong Seokhun kim Vinod Mathew Jaekook kim Department of Materials Science and Engineering Chonnam National University

NiO nanoparticles with average particles size of 30 nm are synthesized using a one-pot metal–organic framework-combustion（MOF-C） technique, for use as an anode material in rechargeable lithium ion batteries（LIBs）. The structural and electronic properties of these nanoparticles are studied using various techniques, including powder X-ray diffraction（PXRD）, transmission electron microscopy（TEM）, scanning electron microscopy（SEM）, X-ray photoelectron spectroscopy（XPS）, and N_2 adsorption/desorption studies. The as-synthesized NiO nanoparticles sustained reversible stable capacities of 748 and 410 mAh/g at applied current densities of 500 and 1000 m A/g, respectively, after 100 cycles. Furthermore, the anode displays a notable rate capability, achieving a stable capacity of ~200 mAh/g at a high current density of10 A/g. These results indicate that the size of the NiO nanoparticles and their high surface area influence their electrochemical properties. Specifically, this combustion strategy is clearly favorable for improving the cyclability and rate capability of various metal oxides in rechargeable battery electrodes.

关键词： Metal-organic frameworks Combustion NiO nanoparticles Lithium ion batteries High rate capability

LongLine:Visual Analytics System for Large-scale Audit Logs

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Visual Informatics 2018年第1期2卷 82-97页

作者： Seunghoon Yoo Jaemin jo Bohyoung kim Jinwook Seo Seoul National University Korea Hankuk University of Foreign Studies Korea

Audit logs are different from other software logs in that they record the most primitive events(i.e.,system calls)in modem operating *** logs contain a detailed trace of an operating system,and thus have received great attention from security experts and system ***,the complexity and size of audit logs,which increase in real time,have hindered analysts from understanding and analyzing *** this paper,we present a novel visual analytics system,LongLine,which enables interactive visual analyses of large-scale audit *** lowers the interpretation barrier of audit logs by employing human-understandable representations(e.g.,file paths and commands)instead of abstract indicators of operating systems(e.g.,file descriptors)as well as revealing the temporal patterns of the logs in a multi-scale fashion with meaningful granularity of time in mind(e.g.,hourly,daily,and weekly).LongLine also streamlines comparative analysis between interesting subsets of logs,which is essential in detecting anomalous behaviors of *** addition,LongLine allows analysts to monitor the system state in a streaming fashion,keeping the latency between log creation and visualization less than one ***,we evaluate our system through a case study and a scenario analysis with security experts.

关键词： Visual Analytics Log Visualization Multidimensional Data

High-power and long-life supercapacitive performance of hierarchical, 3-D urchin-like W18049 nanostructure electrodes

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Nano Research 2016年第3期9卷 633-643页

作者： Sangbaek Park Hyun-Woo Shim Chan Woo Lee Hee jo Song Jae-Chan kim Dong-Wan kim Department of Materials Science and Engineering Seoul National University Seoul 151-744 Republic of Korea School of Civil Environmental and Architectural Engineering Korea University Seou1136-713 Republic of Korea

We report the facile, one-pot synthesis of 3-D urchin-like W18O49 nanostructures （U-WO） via a simple solvothermal approach. An excellent supercapacitive performance was achieved by the U-WO because of its large Brunauer-Emmett- Teller （BET） specific surface area （ca. 123 m2.g-1） and unique morphological and structural features. The U-WO electrodes not only exhibit a high rate-capability with a specific capacitance （Csp） of -235 F·g-1 at a current density of 20 A.g-1, but also superior long-life performance for 1,000 cycles, and even up to 7,000 cycles, showing -176 F·g-1 at a high current density of 40 A.g-1.

关键词： hierarchical structure W18O49 high-power long cycle life supercapacitor

Role of transcription factor acetylation n the regulation of metabolic homeostasis

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Protein & Cell 2015年第11期6卷 804-813页

作者： joo-Man Park Seong-Ho jo Mi-Young kim Tae-Hyun kim Yong-Ho Ahn Department of Biochemistry and Molecular Biology Yonsei University College of Medicine 50-1 Yonsei-ro Seodaemun-gu Seoul 120-752 Republic of Korea Brain Korea 21 PLUS Project for Medical Sciences Yonsei University College of Medicine 50-1 Yonsei-ro Seodaemun-gu Seoul 120-752 Republic of Korea

Post-translational modifications （PTMs） of transcription factors play a crucial role in regulating metabolic homeostasis. These modifications include phosphory- lation, methylation, acetylation, ubiqulUnation, SUMOy- lation, and O-GIcNAcylation. Recent studies have shed light on the importance of lysine acetylation at nonhis- tone proteins including transcription factors. Acetyla- tion of transcription factors affects subcellular distribution, DNA affinity, stability, transcriptional activity, and current investigations are aiming to further expand our understanding of the role of lysine acetyla- tion of transcription factors. In this review, we summarize recent studies that provide new insights into the role of protein lysine-acetylation in the transcriptional regulation of metabolic homeostasis.

关键词： metabolic homeostasis transcriptionfactor post-translational modification type 2 diabetesmellitus

Overview of single-port laparoscopic surgery for colorectal cancers: Past, present, and the future

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World journal of Gastroenterology 2014年第4期20卷 997-100页

作者： Say-June kim Byung-jo Choi Sang Chul Lee Department of Surgery Daejeon St. Mary’s Hospital the Catholic University of Korea

Single-port laparoscopic surgery (SPLS) is implemented through a tailored minimal single incision through which a number of laparoscopic instruments access. Introduction of operation-customized port system, utilization of a camera without a separate external light, and instruments with different lengths has brought the favorable environment for SPLS. However, performing SPLS still creates several hardships compared to multiport laparoscopic surgery; a single-port system inevitably leads to clashing of surgical instruments due to crowding. To overcome such difficulties, investigators has developed novel concepts and maneuvers, including the concept of inverse triangulation and the maneuvers of pivoting, spreading out dissection, hanging suture, and transluminal traction. The final destination of SPLS is expected to be a completely seamless operation, maximizing the minimal invasiveness. Specimen extraction through the umbilicus can undermine cosmesis by inducing a larger incision. Therefore, hybrid laparoscopic technique, which combined laparoscopic surgical technique with natural orifice specimen extraction (NOSE) - i.e., transvaginal or transanal route-, has been developed. SPLS and NOSE seemed to be the best combination in pursuit of minimal invasiveness. In the near future, robotic SPLS with natural orifice transluminal endoscopic surgery’s way of specimen extraction seems to be pursued. It is expected to provide a completely or nearly complete seamless operation regardless of location of the lesion in the abdomen.

关键词： Colorectal neoplasms Colectomy Laparoscopy Natural orifice endoscopic surgery Single-port laparoscopic surgery