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Stiefel–Whitney classes and topological phases in band theory

Chinese Physics B 2019年第11期28卷 1-17页

作者： Junyeong Ahn Sungjoon Park Dongwook kim Youngkuk kim Bohm-jung Yang Department of Physics and Astronomy Seoul National UniversitySeoul 08826Korea Center for Correlated Electron Systems Institute for Basic Science(IBS)Seoul 08826Korea Center for Theoretical Physics(CTP) Seoul National UniversitySeoul 08826Korea

We review the recent progress in the study of topological phases in systems with space–time inversion symmetry *** an anti-unitary symmetry which is local in momentum space and satisfies I2 ST= 1 such as PT in two dimensions(2 D)and three dimensions(3 D) without spin–orbit coupling and C2 T in 2 D with or without spin–orbit coupling, where P, T, C2 indicate the inversion, time-reversal, and two-fold rotation symmetries, respectively. Under IST, the Hamiltonian and the periodic part of the Bloch wave function can be constrained to be real-valued, which makes the Berry curvature and the Chern number vanish. In this class of systems, gapped band structures of real wave functions can be topologically distinguished by the Stiefel–Whitney numbers instead. The first and second Stiefel–Whitney numbers w1 and w2, respectively,are the corresponding invariants in 1 D and 2 D, which are equivalent to the quantized Berry phase and the Z2 monopole charge, respectively. We first describe the topological phases characterized by the first Stiefel–Whitney number, including1 D topological insulators with quantized charge polarization, 2 D Dirac semimetals, and 3 D nodal line semimetals. Next we review how the second Stiefel–Whitney class characterizes the 3 D nodal line semimetals carrying a Z2 monopole *** particular, we explain how the second Stiefel–Whitney number w2, the Z2 monopole charge, and the linking number between nodal lines are related. Finally, we review the properties of 2 D and 3 D topological insulators characterized by the nontrivial second Stiefel Whitney class.

关键词： topological semimetal

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Preparation and characterization of Li_(4)Ti_(5)O_(12) synthesized using hydrogen titanate nanowire for hybrid super capacitor

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Journal of Advanced Ceramics 2013年第3期2卷 285-290页

作者： Jong Hyun kim jung Rag YOON R&D Center Samwha Capacitor Co.Ltd.YonginGyeonggi 449-884R.O.Korea

The electrical characteristics of hybrid super capacitor were evaluated by synthesizing LTO(Li_(4)Ti_(5)O_(12))using TiO_(2) having a hydrogen titanate nanowire *** of the hydrogen titanate nanowire was implemented by using TiO_(2) having size of 60 nm and NaOH,and performing synthesis at 70℃for 6 h with a sonochemical *** compound was synthesized at 150℃for 36 h and at 180℃for 36 h respectively by using the hydrogen titanate nanowire and LiOH·H2O as starting materials with a hydrothermal *** final LTO compound was synthesized at 700℃for 6 h using a solid-state *** a result of manufacturing the hybrid super capacitor using LTO synthesized at 180℃for 36 h with the hydrothermal method,a capacity of 198 mA·h/g has been achieved compared to a theoretical capacity of 172 mA·h/g of existing LTO,and thus,the capacity has been increased by about 13%.Further,such excellent cycle performance has ensured its possibility as a high-capacity capacitor.

关键词： LTO(Li4Ti5O12) lithium titanate oxide hydrogen titanate nanowire hybrid super capacitor

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Multi-View Multi-Modal Head-Gaze Estimation for Advanced Indoor User Interaction

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Computers, Materials & Continua 2022年第3期70卷 5107-5132页

作者： jung-Hwa kim Jin-Woo Jeong Department of Computer Engineering Kumoh National Institute of TechnologyGumi39177Korea Department of Data Science Seoul National University of Science and TechnologySeoul01811Kore

Gaze estimation is one of the most promising technologies for supporting indoor monitoring and interaction ***,previous gaze estimation techniques generally work only in a controlled laboratory environment because they require a number of high-resolution eye *** makes them unsuitable for welfare and healthcare facilities with the following challenging characteristics:1)users’continuous movements,2)various lighting conditions,and 3)a limited amount of available *** address these issues,we introduce a multi-view multi-modal head-gaze estimation system that translates the user’s head orientation into the gaze *** proposed system captures the user using multiple cameras with depth and infrared modalities to train more robust gaze estimators under the aforementioned *** this end,we implemented a deep learning pipeline that can handle different types and combinations of *** proposed system was evaluated using the data collected from 10 volunteer participants to analyze how the use of single/multiple cameras and modalities affect the performance of head-gaze *** various experiments,we found that 1)an infrared-modality provides more useful features than a depth-modality,2)multi-view multi-modal approaches provide better accuracy than singleview single-modal approaches,and 3)the proposed estimators achieve a high inference efficiency that can be used in real-time applications.

关键词： Human-computer interaction deep learning head-gaze estimation indoor monitoring

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Chinese Medicines Reported to Have Effects on Contact Dermatitis in the Last 20 Years

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Chinese Journal of Integrative Medicine 2018年第1期24卷 64-71页

作者： Youngchul jung Byungju kim Mi Heon Ryu Hyungwoo kim School of Korean Medicine Pusan National University School of Dentistry Pusan National University

Contact dermatitis （CD） is one of the most common skin diseases in industrialized countries. Chinese medicines （CMs） have been investigated worldwide as complementary and alternative medicines for corticosteroids, which are the first choice for treatment of inflammatory skin diseases owing to their favorable efficacy. This article describes the CMs that have been reported to have anti-dermatitis effects against CD in the last 20 years.

关键词： contact dermatitis herbal Chinese medicine

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High-frequency acoustic backscattering characteristics for acoustic detection of the red tide species Akashiwo sanguinea and Alexandrium affine

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Journal of Oceanology and Limnology 2019年第4期37卷 1268-1276页

作者： kim Hansoo KANG Donhyug jung Seung Won kim Mira Maritime Security and Safety Research Center Korea Institute of Ocean Science & Technology (KIOST) Busan 49111 Korea Department of Ocean System Engineering Jeju National University Jeju 63243 Korea Library of Marine Samples Korea Institute of Ocean Science & Technology (KIOST) Geoje 53201 Korea

Harmful algal blooms (HABs), caused by the overgrowth of certain phytoplankton species, have negative effects on marine environments and coastal fisheries. In addition to cell-counting methods using phytoplankton nets, a hydroacoustic technique based on acoustic backscattering has been proposed for the detection of phytoplankton blooms. However, little is known of the acoustic properties of HAB species. In this study, as essential data to support this technique, we measured the acoustic properties of two HAB species, Akashiwo sanguinea and Alexandrium affine, which occur in the South Sea off the coast of Korea. Due to the small size of the target, we used ultrasound for the measurements. Experiments were conducted under laboratory and field conditions. In the laboratory experiment, the acoustic signal received from each species was directly proportional to the cell abundance. We derived a relationship between the cell abundance and acoustic signal received for each species. The measured signals were compared to predictions of a fluid sphere scattering model. When A. sanguinea blooms appeared at an abundance greater than 3 500 cells/mL, the acoustic signals varied with cell abundance, showing a good correlation. These results confirm that acoustic measurements can be used to detect HAB species.

关键词： acoustic backscattering Akashiwo sanguinea Alexandrium affine fluid-sphere scattering model harmful algal blooms (HABs) red tide

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Patient safety culture and handoff evaluation of nurses in small and medium-sized hospitals

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International Journal of Nursing Sciences 2021年第1期8卷 58-64,I0004页

作者： jung Hee kim jung Lim Lee Eun Man kim Department of Nursing Science Shinsung UniversityChungnamSouth Korea Department of Nursing Daejeon UniversityDaejeonSouth Korea Department of Nursing Science Sun Moon UniversityChungnamSouth Korea

Objectives:This study was conducted to investigate the current status of handoffs,perception of patient safety culture,and degrees of handoff evaluation in small and medium-sized hospitals and identified factors that make a difference in handoff ***:This is a descriptive study.425 nurses who work at small and medium-sized hospitals in South Korea were included in our *** completed a set of self-reporting questionnaires that evaluated demographic data,handoff-related characteristics,perception of patient safety culture,and handoff ***:Results showed that the overall score of awareness of a patient safety culture was 3.65±0.45,the level was *** score of handoff evaluation was 5.24±*** nurses experienced errors in handoff and most nurses had no guidelines and checklist in the *** evaluation differed significantly according to the level of education,work patterns,duration of hospital employment,handoff method,degree of satisfaction with the current handoff method,errors occurring at the time of handoff,handoff guidelines,and appropriateness of handoff education time(P<0.05).Conclusion:For handoff improvement,guidelines and standards should be *** is necessary to develop a structured handoff education *** formal handoff education should be implemented to spread knowledge uniformly.

关键词： Evaluation studies Handoff Hospital nursing staff Patient safety

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Determination of diffusion coefficient by image-based fluorescence recovery after photobleaching and single particle tracking system implemented in a single platform

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Journal of Innovative Optical Health Sciences 2021年第2期4卷 93-101页

作者： Donghee Lee Jeonghoon Lee jung Kyung kim Department of Genetics Cell Biology and Anatomy University of Nebraska Medical CenterOmahaNE 68198USA School of Mechanical Engineering KOREA TECH Cheonan 31253Republic of Korea School of Mechanical Engineering and Department of Integrative Biomedical Science and Engineering Graduate School Kookmin University Seoul 02707Republic of Korea

Fluorescence recovery after photobleaching(FRAP)and single particle tracking(SPT)techni-ques determine the diffusion coefficient from average diffusive motion of high-concentration molecules and from trajectories of low-concentration single molecules,*** dif-fusion coefficients measured by FRAP and SPT techniques for the same biomolecule on cell membrane have exhibited inconsistent values across laboratories and platforms with larger dif-fusion coefficient determined by FRAP,but the sources of the inconsistency have not been investigated ***,we designed an image-based FRAP-SPT system and made a direct comparison between FRAP and SPT for diffusion coefficient of submicron particles with known theoretical values derived from Stokes-Einstein equation in aqueous *** combined iFRAP-SPT technique allowed us to measure the diffusion coefficient of the same fluorescent particle by utilizing both techniques in a single platform and to scrutinize inherent errors and artifacts of *** results reveal that diffusion coefficient overestimated by FRAP is caused by inaccurate estimation of the bleaching spot size and can be corrected by simple image *** iFRAP-SPT technique can be potentially used for not only cellular membrane dynamics but also for quantitative analysis of the spatiotemporal distribution of the solutes in small scale analytical devices.

关键词： Diffusion coefficient fluorescence recovery after photobleaching(FRAP) single particle tracking(SPT)

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Modeling in Multi-Resolution and Its Applications

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Journal of Computer Science & Technology 2006年第2期21卷 272-278页

作者： Sungchan kim Kunwoo Lee Taesik Hong Moonki jung School of Mechanical and Aerospace Engineering Seoul National University San 56-1 Sillim-Dong Gwanak-Gu Seoul 151-752 Korea

It is becoming common for many designers to work together on very complex assemblies in a collaborative environment. To work efficiently in this environment, the capabilities to simplify the portions of an assembly and to reset it to the original resolution should be added to the current CAD systems. Thus operators realizing multi-resolution on B-rep were proposed in previous work. This paper illustrates a prototype multi-resolution system to integrate the proposed operators and its applications. The multi-resolution system can be used in similarity comparisons to reduce the calculation load and to get the full comparison result in the overall shape. Then the features recognized with this system can be used in more detailed comparisons. This system also can be used conceptually to solve security problems in collaborative design.

关键词： collaborative design level of detail multi-resolution similarity comparison

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Continuum understanding of twin formation near grain boundaries of FCC metals with low stacking fault energy

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npj Computational Materials 2017年第1期3卷 275-283页

作者： Jaimyun jung Jae Ik Yoon jung Gi kim Marat I.Latypov Jin You kim Hyoung Seop kim Department of Materials Science and Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea GT-CNRS UMI 2958 Georgia TechLorraine 57070 MetzFrance Pohang Research Laboratory Steel Products Research Group 1POSCOPohang 790-785Republic of Korea Center for High Entropy Alloys Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea

Deformation twinning from grain boundaries is often observed in face-centered cubic metals with low stacking fault *** of the possible factors that contribute to twinning origination from grain boundaries is the intergranular interactions during ***,the influence of mechanical interaction among grains on twin evolution has not been fully *** spite of extensive experimental and modeling efforts on correlating microstructural features with their twinning behavior,a clear relation among the large aggregate of grains is still *** this work,we characterize the micromechanics of grain-to-grain interactions that contribute to twin evolution by investigating the mechanical twins near grain boundaries using a full-field crystal plasticity simulation of a twinning-induced plasticity steel deformed in uniaxial tension at room *** are first observed through electron backscatter diffraction technique to obtain data to reconstruct a statistically equivalent microstructure through synthetic microstructure ***-to-grain micromechanical response is analyzed to assess the collective twinning behavior of the microstructural volume element under tensile *** of the simulated results reveal that grain interactions are capable of changing the local mechanical behavior near grain boundaries by transferring strain across grain boundary or localizing strain near grain boundary.

关键词： grain microstructure steel

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Fe_(3)GeTe_(2):a site-differentiated Hund metal

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npj Computational Materials 2022年第1期8卷 2355-2360页

作者： Taek jung kim Siheon Ryee Myung Joon Han Department of Physics KAISTDaejeon34141Republic of Korea I.Institute of Theoretical Physics University of HamburgNotkestrasse 9-11Hamburg22607Germany

Magnetism in two-dimensional(2D)van der Waals(vdW)materials has lately attracted considerable attention from the point of view of both fundamental science and device ***,establishing a detailed and solid understanding of their magnetism is the key first step toward various *** Fe_(3)GeTe_(2)is a representative ferromagnetic(FM)metal in this family,many aspects of its magnetic and electronic behaviors still remain ***,we report our new finding that Fe_(3)GeTe_(2)is a special type of correlated metal known as“Hund metal”.Furthermore,we demonstrate that Hund metallicity in this material is quite unique by exhibiting remarkable site dependence of Hund correlation strength,hereby dubbed“site-differentiated Hund metal”.Within this new picture,many of the previous experiments can be clearly understood,including the ones that were seemingly contradictory to one another.

关键词： strength establishing metallic

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