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Origin of superior low-cycle fatigue resistance of an interstitial metastable high-entropy alloy

Journal of Materials Science & Technology 2022年第20期115卷 115-128页

作者： Seyed Amir Arsalan Shams jae Wung Bae jae nam kim Hyoung Seop kim Taekyung Lee Chong Soo Lee Graduate Institute of Ferrous Technology Pohang University of Science and TechnologyPohang 37673Republic of Korea Department of Materials Science and Engineering Pohang University of Science and TechnologyPohang 37673Republic of Korea School of Mechanical Engineering Pusan National UniversityBusan 46241Republic of Korea

In this study, the deformation behaviors and related microstructural evolutions were investigated in either monotonic or cyclic deformation modes in an interstitial metastable high-entropy alloy. These investigations aimed to reveal the mechanisms underlying the superior low-cycle fatigue(LCF) life of this alloy.A thermomechanical process was applied to induce fine-grained(FG) and coarse-grained(CG) microstructures in Fe–30Mn–10Co–10Cr–0.4C(atomic percentage) alloy. Their superior combination of strength and ductility was attributed to the appearance of deformation-induced ε-martensite and the presence of carbon. The CG alloy showed a greater volume fraction of ε-martensite than the FG alloy in the monotonic deformation mode, and vice versa in the cyclic mode. Such a disparity was interpreted in light of the back-stress effect of the relaxed γ-grain boundaries in the latter mode. Meanwhile, the γ-to-ε phase transformation under cyclic loading at low strain amplitudes(0.4%) barely led to an improved fatigue life as compared with that at higher strain amplitudes(≥ 0.55%). The high reversibility of partial dislocation motions under cyclic loading and delaying the formation of dislocation cells through the martensitic transformation could explain why the alloys investigated in this study exhibited a superior LCF life compared with high-entropy alloys reported in previous studies.

关键词： High-entropy alloy Transformation-induced plasticity Monotonic deformation Cyclic deformation Low-cycle fatigue Stacking faults

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Random pinhole attenuator for high-power laser beams

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High Power Laser Science and Engineering 2024年第3期12卷 116-121页

作者： Seong Cheol Park Hyeok Yun Jin Woo Yoon Seong Ku Lee jae Hee Sung Il Woo Choi Chang Hee nam Kyung Taec kim Department of Physics and Photon Science Gwangju Institute of Science and TechnologyGwangjuRepublic of Korea Center for Relativistic Laser Science Institute for Basic ScienceGwangjuRepublic of Korea Advanced Photonics Research Institute Gwangju Institute of Science and TechnologyGwangjuRepublic of Korea

The intensity attenuation of a high-power laser is a frequent task in the measurements of optical *** intensity can be attenuated by inserting an optical element,such as a partial reflector,polarizer or absorption *** devices are,however,not always easily applicable,especially in the case of ultra-high-power lasers,because they can alter the characteristics of a laser beam or become easily *** this study,we demonstrated that the intensity of a laser beam could be effectively attenuated using a random pinhole attenuator(RPA),a device with randomly distributed pinholes,without changing the beam *** this device,a multi-PW laser beam was successfully attenuated and the focused beam profile was measured without any alterations of its *** addition,it was confirmed that the temporal profile of a laser pulse,including the spectral phase,was ***,the RPA possesses significant potential for a wide range of applications.

关键词： high-power laser intensity attenuation laser diagnostics

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Sleep Posture Classification Using RGB and Thermal Cameras Based on Deep Learning Model

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Computer Modeling in Engineering & Sciences 2024年第8期140卷 1729-1755页

作者： Awais Khan Chomyong kim Jung-Yeon kim Ahsan Aziz Yunyoung nam Department of ICT Convergence Soonchunhyang UniversityAsan31538Korea ICT Convergence Research Center Soonchunhyang UniversityAsan31538Korea Emotional and Intelligent Child Care Convergence Research Center Soonchunhyang UniversityAsan31538Korea

Sleep posture surveillance is crucial for patient comfort,yet current systems face difficulties in providing compre-hensive studies due to the obstruction caused by *** posture assessment remains challenging because of the complex nature of the human body and variations in sleep ***,this study introduces an innovative method utilizing RGB and thermal cameras for comprehensive posture classification,thereby enhancing the analysis of body position and *** method begins by capturing a dataset of sleep postures in the form of videos using RGB and thermal cameras,which depict six commonly adopted postures:supine,left log,right log,prone head,prone left,and prone *** study involves 10 participants under two conditions:with and without ***,the database is normalized into a video *** subsequent step entails training a fine-tuned,pretrained Visual Geometry Group(VGG16)and ResNet50 *** the third phase,the extracted features are utilized for *** fourth step of the proposed approach employs a serial fusion technique based on the normal distribution to merge the vectors derived from both the RGB and thermal ***,the fused vectors are passed to machine learning classifiers for final *** dataset,which includes human sleep postures used in this study’s experiments,achieved a 96.7%accuracy rate using the Quadratic Support Vector Machine(QSVM)without the ***,the Linear SVM,when utilized with a blanket,attained an accuracy of 96%.When normal distribution serial fusion was applied to the blanket features,it resulted in a remarkable average accuracy of 99%.

关键词： Human sleep posture VGG16 deep learning ResNet50 fusion machine learning

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Driving inward growth of lithium metal in hollow microcapsule hosts by heteroatom‐controlled nucleation

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Carbon Energy 2024年第8期6卷 262-272页

作者： Siwon kim Hong Rim Shin Ki jae kim Min‐Sik Park Jong‐Won Lee Division of Materials Science and Engineering Hanyang UniversitySeoulRepublic of Korea Department of Energy Science and Engineering Daegu Gyeongbuk Institute of Science and Technology(DGIST)DaeguRepublic of Korea Department of Energy Science Sungkyunkwan UniversitySuwonRepublic of Korea Department of Advanced Materials Engineering for Information and Electronics Integrated Education for Frontier Science and Technology(BK21 Four)Kyung Hee UniversityYonginRepublic of Korea

The application of Li metal anodes in rechargeable batteries is impeded by safety issues arising from the severe volume changes and formation of dendritic Li ***‐dimensional hollow carbon is receiving increasing attention as a host material capable of accommodating Li metal inside its cavity;however,uncontrollable and nonuniform deposition of Li remains a *** this study,we synthesize metal–organic framework‐derived carbon microcapsules with heteroatom clusters(Zn and Ag)on the capsule walls and it is demonstrated that Ag‐assisted nucleation of Li metal alters the outward‐to‐inward growth in the microcapsule ***‐incorporated microcapsules are prepared via chemical etching of zeolitic imidazole framework‐8 polyhedra and are subsequently decorated with Ag by a galvanic displacement reaction between Ag^(+)and metallic *** introduced Ag significantly reduces the energy barrier and increases the reaction rate for Li nucleation in the microcapsule host upon Li *** combined electrochemical,microstructural,and computational studies,we verify the beneficial role of Ag‐assisted Li nucleation in facilitating inward growth inside the cavity of the microcapsule host and,in turn,enhancing electrochemical *** study provides new insights into the design of reversible host materials for practical Li metal batteries.

关键词： hollow carbon hosts lithium metal batteries lithium plating metal-organic frameworks nucleation

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Modification strategies improving the electrochemical and structural stability of high-Ni cathode materials

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Journal of Energy Chemistry 2024年第9期96卷 185-205页

作者： Yoon Bo Sim Hami Lee Junyoung Mun Ki jae kim Department of Energy Science Sungkyunkwan UniversitySuwon 16419Republic of Korea School of Advanced Materials Science and Engineering Sungkyunkwan UniversitySuwon 16419Republic of Korea SKKU Institute of Energy Science and Technology(SIEST) Sungkyunkwan UniversitySuwon 16419Republic of Korea

With the increasing spotlight in electric vehicles,there is a growing demand for high-energy-density batteries to enhance driving ***,several studies have been conducted on high-energy-density LiNi_(x)Co_(y)Mn_(z)O_(2)***,there is a limit to permanent performance deterioration because of side reactions caused by moisture in the atmosphere and continuous microcracks during cycling as the Ni content to express high energy increases and the content of Mn and Co that maintain structural and electrochemical stabilization *** direct modification of the surface and bulk regions aims to enhance the capacity and long-term performance of high-Ni cathode ***,an efficient modification requires a study based on a thorough understanding of the degradation mechanisms in the surface and bulk *** this review,a comprehensive analysis of various modifications,including doping,coating,concentration gradient,and single crystals,is conducted to solve degradation issues along with an analysis of the overall degradation mechanism occurring in high-Ni cathode *** also summarizes recent research developments related to the following modifications,aims to provide notable points and directions for post-studies,and provides valuable references for the commercialization of stable high-energy-density cathode materials.

关键词： High energy density High-Ni cathode materials Degradation Structural stability Lithium-ion battery

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Comparative efficacy and optimal duration of first-line antibiotic regimens for acute otitis media in children and adolescents:a systematic review and network meta-analysis of 89 randomized clinicaltrials

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World Journal of Pediatrics 2024年第3期20卷 219-229页

作者： Min Seo kim jae Han kim Seohyun Ryu Seung Won Lee Dong Keon Yon Eunyoung kim Ai Koyanagi Elena Dragioti jae Il Shin Lee Smith Samsung Advanced Institute forHealth Sciences&Technology(SAIHST) Samsung Medical CenterSungkyunkwan UniversitySeoulRepublic of Korea Yonsei University Collegeof Medicine SeoulRepublicof Korea Department of Precision Medicine Sungkyunkwan University School of MedicineSuwonRepublic of Korea Center for Digital Health Medical Science Research InstituteKyung Hee University College of MedicineSeoulRepublic of Korea Evidence-Based Research Laboratory Department of Clinical Pharmacy and Pharmaceutical CareCollege of PharmacyChung-Ang UniversitySeoulRepublic of Korea Parc Sanitari Sant Joan de Deu/CIBERSAM/ISCIII Universitat de BarcelonaFundacio Sant Joan de Déu.Sant Boi de LlobregatBarcelonaSpain ICREA Pg.Lluis Companys 23BarcelonaSpain Pain and Rehabilitation Centre and Department of Medical and Health SciencesLinkoping University58185 LinkopingSweden Department of Pediatrics Yonsei University College of MedicineYonsei-ro 50Seodaemun-gu8044Seoul 03722Republic of Korea Centre for Health Performanceand WellbeingAnglia Ruskin UniversityCambridge CB11PTUK Research Laboratory Psychology of Patients Families&Health ProfessionalsDepartment of NursingSchool of Health SciencesUniversity of IoanninaIoannina 45500Greece

Introduction Antibiotic use for acute otitis media(AOM)is one of the major sources of antimicrobial ***,the effective minimal antibiotic duration for AOM remains ***,guidelines often recommend broad ranges(5-10 days)of antibiotic use,yet the clinical impact of such a wide window has not been *** We systematically searched PubMed/MEDLINE,Embase,Scopus,Web of Science,and Cochrane Library from database inception to 6 October *** meta-analysis was conducted on randomized controlled trials that assessed antibiotic treatment for AOM in children(PROSPERO CRD42020196107).Results For amoxicillin and amoxicillin-clavulanate,7-day regimens were noninferior to 10-day regimens in clinical responses[amoxicillin:risk ratio(RR)0.919(95%CI 0.820-1.031),amoxicillin-clavulanate:RR 1.108(0.957-1.282)],except for≤2 *** the third-generation cephalosporins,7-day and 10-day regimens had similar clinical responses compared to placebo[7-day:RR 1.420(1.190-1.694),10-day:RR 1.238(1.125-1.362)compared to placebo].However,5-day regimens of amoxicillin-clavulanate and third-generation cephalosporins were inferior to 10-day *** to amoxicillin,a shorter treatment duration was tolerable with *** Our findings indicated that 1O days of antibiotic use may be unnecessarily long,while the treatment duration should be longer than 5 ***,5-day regimens would be sufficient for a modest treatment *** findings revealed that the current wide range of recommended antibiotic durations may have influenced the clinical outcome of AOM,and a narrower antibiotic duration window should be re-established.

关键词： Amoxicillin-potassium Amoxicillin Antibacterial agents Cephalosporins Duration of therapy

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Opportunities and challenges in cathode development for non-lithium-ion batteries

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eScience 2024年第4期4卷 1-6页

作者： Haegyeom kim jae Chul kim Materials Sciences Division Lawrence Berkeley National Laboratory94720CAUSA Department of Chemical Engineering and Materials Science Stevens Institute of Technology07030NJUSA

Lithium(Li)-ion batteries have stimulated the societal transformation to clean energy *** carry-on electricity is revolutionizing how society communicates,functions,and evolves efficiently by enabling mobile electronics,zero-emission electric vehicles,and stationary energy *** preparation for the sustainable energy future,however,there are growing concerns about depleting critical elements used in the Li technology(e.g.,lithium,cobalt,and nickel),especially for large-scale applications that will accelerate the rate of elemental *** non-Li-based rechargeable batteries composed of earth-abundant elements,such as sodium,potassium,magnesium,and calcium,have been proposed and explored as alternative systems to promote sustainable development of energy *** this perspective,we discuss challenges in Li-ion batteries in the sustainability aspect and provide our opinions on the potential applications of non-Li-based *** also highlight the current status,important progress,and remaining challenges of the Li-alternative technologies.

关键词： Batteries Sodium Potassium Lithium Multi-valent Energy storage

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SOME LIOUVILLE-TYPE THEOREMS FOR THE STATIONARY 3D MAGNETO-MICROPOLAR FLUIDS

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Acta Mathematica Scientia 2024年第6期44卷 2296-2306页

作者： jae-Myoung kim Seungchan KO Department of Mathematics Education Andong National University Department of Mathematics Inha University

In this paper,we prove some Liouville-type theorems for the stationary magnetomicropolar fluids under suitable conditions in three space *** first prove that the solutions are trivial under the assumption of certain growth conditions for the mean oscillations of the *** then we show similar results assuming that the solutions are contained in Lp（R3） with p ∈ [2,9/2).Finally,we show the same result for lower values of p ∈ [1,9/4) with the further assumption that the solutions vanish at infinity.

关键词： Liouville-type theorem stationary magneto-micropolar equations

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Reconstruction of cervical necrotizing fasciitis defect with the modified keystone flap technique:Two case reports

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World Journal of Clinical Cases 2024年第7期12卷 1305-1312页

作者： Wonseok Cho Eun A Jang Kyu nam kim Department of Plastic and Reconstructive Surgery Kangbuk Samsung HospitalSungkyunkwan University School of MedicineSeoul 03181South Korea

BACKGROUND Cervical necrotizing fasciitis(CNF)is a rare,aggressive form of deep neck space infection with significant morbidity and mortality *** surgical debridement acts as the cornerstone of CNF treatment;however,it often results in defects requiring complex *** SUMMARY We report two cases in which the keystone flap(KF)was used for CNF defect coverage:Case 1,an 85-year-old patient with CNF in the anterior neck,and Case 2,a 54-year-old patient with CNF in the posterior *** patients received empirical intravenous antibiotic therapy and underwent serial debridement,enabling adequate wound preparation and *** final defect size measured 5.5 cm×12 cm in Case 1 and 6 cm×11 cm in Case *** defect coverage,we employed an 8 cm×19 cm type II KF based on perforators from the superior thyroid artery in Case 1 and a 9 cm×18 cm type II KF based on perforators from the transverse cervical artery in Case *** flaps showed complete *** postoperative complications occurred in both cases,and favorable outcomes were observed at 7-and 6-month follow-ups in case 1 and 2,*** We effectively treated CNF-associated defects using the KF technique;KF is viable for covering CNF defects in carefully selected cases.

关键词： Fasciitis Necrotizing Debridement Plastic surgery Dermatologic surgical procedures Case report

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Electrochemically Deposited CZTSSe Thin Films for Monolithic Perovskite Tandem Solar Cells with Efficiencies Over 17%

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Energy & Environmental Materials 2024年第1期7卷 147-152页

作者： Sun Kyung Hwang Ik jae Park Se Won Seo jae Hyun Park So Jeong Park Jin Young kim Department of Materials Science and Engineering Seoul National UniversitySeoul 08826Korea Department of Applied Physics Sookmyung Women's UniversitySeoul 04310Korea Research Institute of Advanced Materials and Systems Sookmyung Women's UniversitySeoul 04310Korea Research Institute of Advanced Materials(RIAM) Seoul National UniversitySeoul 08826Korea

In spite of the high potential economic feasibility of the tandem solar cells consisting of the halide perovskite and the kesterite Cu2ZnSn(S,Se)4(CZTSSe),they have rarely been demonstrated due to the difficulty in implementing solution-processed perovskite top cell on the rough surface of the bottom ***,we firstly demonstrate an efficient monolithic two-terminal perovskite/CZTSSe tandem solar cell by significantly reducing the surface roughness of the electrochemically deposited CZTSSe bottom *** surface roughness(R_(rms))of the CZTSSe thin film could be reduced from 424 to 86 nm by using the potentiostatic mode rather than using the conventional galvanostatic mode,which can be further reduced to 22 nm after the subsequent ion-milling *** perovskite top cell with a bandgap of 1.65 eV could be prepared using a solution process on the flattened CZTSSe bottom cell,resulting in the efficient perovskite/CZTSSe tandem solar *** the current matching between two subcells involving the thickness control of the perovskite layer,the best performing tandem device exhibited a high conversion efficiency of 17.5%without the hysteresis effect.

关键词： CZTSSe monolithic tandem solar cells perovskite solution process surface roughness control

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