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Enhancement of magnetic properties of hot pressed/die-upset Dy-free Nd-Fe-B magnets with Cu/Nd coating by wet process

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Rare Metals 2020年第1期39卷 48-54页

作者： Jeehye kwon Dajeong Lee Dayoung Yoo Seongkyu Park Hee-Ryoung Cha hae-woong kwon Junggoo Lee Dongyun Lee Department of Advanced Circuit Interconnection Pusan National UniversityBusan46241Republic of Korea Department of Nano Fusion Technology Pusan National UniversityBusan46241Republic of Korea Powder and Ceramics Department Korea Institute of Machinery and MaterialsChangwon51508Republic of Korea Department of Materials Science and Engineering Pukyong National UniversityBusan48513Republic of Korea Department of Nanoenergy Engineering Pusan National UniversityBusan46241Republic of Korea

A grain boundary diffusion process(GBDP)was adopted to improve magnetic properties of Dy-free highly coercive Nd-Fe-B permanent magnet by coating thin layers of Nd and Cu in grain *** GBDP of Nd and Cu,Nd and Cu were coated by wet process,e.g.,electrochemical and electroless on Nd-Fe-B magnets,which was fabricated by hot-deformed/die-upset with meltspun *** treatment was performed for 20 min at 600℃followed by several different cooling *** cooling conditions after heat treatment were varied to understand distribution and micros tructural effects of Nd and Cu species in grain *** coercivity increased from 1.565 to 1.637 T in oil cooling rate but remanence decreased,while remanence jumped with little decrease in coercivity in furnace *** tructure analyses suggested that the coercivity was closely related to the cooling rate as well as distribution of *** mechanism of coercivity enhancement due to the cooling rate was discussed based on the results presented here and those in the literature.

关键词： Magnetic materials Electrochemical deposition Diffusion Scanning electron microscopy Coercivity

Towards high-performance and robust anion exchange membranes(AEMs)for water electrolysis:Super-acid-catalyzed synthesis of AEMs

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Journal of Energy Chemistry 2024年第6期93卷 478-510,I0012页

作者： Geun woong Ryoo Sun Hwa Park Ki Chang kwon Jong Hun Kang Ho Won Jang Min Sang kwon Department of Materials Science and Engineering Research Institute of Advanced Materials(RIAM)Seoul National UniversitySeoul 08826Republic of Korea Interdisciplinary Materials Measurement Institute Korea Research Institute of Standards and Science(KRISS)Daejeon 34113Republic of Korea Department of Chemical and Biological Engineering and Institute of Chemical ProcessSeoul National UniversitySeoul 08826Republic of Korea Department of Applied Measurement Science University of Science and TechnologyDaejeon 34113Republic of Korea

The increasing demand for hydrogen energy to address environmental issues and achieve carbon neutrality has elevated interest in green hydrogen production,which does not rely on fossil *** various hydrogen production technologies,anion exchange membrane water electrolyzer(AEMWE)has emerged as a next-generation technology known for its high hydrogen production efficiency and its ability to use non-metal ***,this technology faces significant challenges,particularly in terms of the membrane durability and low ionic *** address these challenges,research efforts have focused on developing membranes with a new backbone structure and anion exchange groups to enhance durability and ionic ***,the super-acid-catalyzed condensation(SACC)synthesis method stands out due to its user convenience,the ability to create high molecular weight(MW)polymers,and the use of oxygen-tolerant organic *** the synthesis of anion exchange membranes(AEMs)using the SACC method began in 2015,and despite growing interest in this synthesis approach,there remains a scarcity of review papers focusing on AEMs synthesized using the SACC *** review covers the basics of SACC synthesis,presents various polymers synthesized using this method,and summarizes the development of these polymers,particularly their building blocks including aryl,ketone,and anion exchange *** systematically describe the effects of changes in the molecular structure of each polymer component,conducted by various research groups,on the mechanical properties,conductivity,and operational stability of the *** review will provide insights into the development of AEMs with superior performance and operational stability suitable for water electrolysis applications.

关键词： Green hydrogen production Water electrolysis Anion exchange membrane water electrolyzer(AEMWE) Anion exchange membranes(AEMs) Super-acid-catalyzed condensation(SACC)

Surgical Repair of Ventricular Septal Defect in Neonates: Indications and Outcomes

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Congenital Heart Disease 2024年第1期19卷 69-83页

作者： Jae Hong Lee Sungkyu Cho Jae Gun Kwak Hye Won kwon woong-Han Kim Mi Kyoung Song Sang-Yun Lee Gi Beom Kim Eun Jung Bae Department of Thoracic and Cardiovascular Surgery Research Institute for Convergence of Biomedical Science and TechnologyPusan National University Yangsan HospitalYangsanKorea Department of Thoracic and Cardiovascular Surgery Seoul National University Children’s HospitalSeoulKorea Department of Pediatrics Seoul National University Children’s HospitalSeoulKorea

Background:The optimal surgical timing and clinical outcomes of ventricular septal defect(VSD)closure in neo-nates remain *** aimed to evaluate the clinical outcomes of VSD closure in neonates(age≤30 days).Methods:We retrospectively reviewed 50 consecutive neonates who underwent VSD closure for isolated VSDs between August 2003 and June *** for the procedure included congestive heart failure/failure to thrive and pulmonary *** adverse events(MAEs)were deﬁned as the composite of all-cause mortality,reoperation,persistent atrioventricular block,and signiﬁcant(≥grade 2)valvular ***:The median age and body weight at operation were 26.0 days(interquartile range[IQR],18.8–28.3)and 3.7 kg(IQR,3.3–4.2),*** median follow-up duration was 110.4 months(IQR,56.8–165.0).Seven patients required preoperative respiratory support,andﬁve had signiﬁcant(≥grade 2)preoperative valvular *** early mortality occurred due to irreversible cardiogenic shock;no late mortality was *** reopera-tion was due to hemodynamically signiﬁcant residual VSD at 103.8 months *** overall survival,freedom from reoperation,and freedom from MAE at 15-years were 98.0%,96.3%,and 94.4%,***-operative mechanical ventilation was associated with a longer duration of postoperative mechanical ventilation(p<0.001)and a longer length of intensive care unit stay(p<0.001).Conclusions:VSD closure with favorable outcomes without morbidities is feasible even in ***,neonates requiring preoperative respiratory support may require careful postoperative management considering the long-term postoperative ***,surgical VSD closure might be indicated earlier in neonates with respiratory compromise.

关键词： Ventricular septal defect neonate early surgery neonatal surgery

Improving the electrochemical stability of AZ31 Mg alloy in a 3.5wt.%NaCl solution via the surface functionalization of plasma electrolytic oxidation coating

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Journal of Magnesium and Alloys 2022年第5期10卷 1311-1325页

作者： Mosab Kaseem Tehseen Zehra Burak Dikici Ali Dafali hae woong Yang Young Gun Ko Department of Nanotechnology and Advanced Materials Engineering Sejong UniversitySeoul 05006Republic of Korea Department of Metallurgical and Materials Engineering Ataturk UniversityErzurum 25240Turkey Faculty of Sciences Oujda Department of ChemistryMohamed the First UniversityOujdaMorocco Pohang Institute of Metal Industry Advancement Pohang 37666Republic of Korea Materials Electrochemistry Group School of Materials Science and EngineeringYeungnam UniversityGyeongsan 38541Republic of Korea

The unique interactions between hexadecanoic acid(HA)and albumin(ALB)molecules on the surface of the porous layer of AZ31 Mg alloy were exploited to fabricate a novel hybrid composite film with excellent electrochemical stability in a 3.5 wt.%Na Cl ***,the inorganic layer(IL)obtained by plasma electrolytic oxidation of AZ31 Mg alloy in an alkaline-phosphate-WO_(3)electrolyte was soaked in an organic solution composed of ALB and HA for 10 and 24 h at 60℃.Although albumin and HA may coexist on the same surface of IL,the higher reactivity of ALB molecules would prevent the formation of a thick layer of *** donor-acceptor complexes formed due to the unique interactions between ALB and/or HA and IL surface would reduce the area exposed to the corrosive species which in turn would efficiently protect the substrate from *** porous structure of the IL would provide preferable sites for the physical and chemical locking triggered by charge-transfer phenomena,leading to the inhomogeneous nucleation and crystal growth of a flowery flakes-like organic *** calculations were performed to reveal the primary bonding modes between the ALB,HA,and IL and to assess the mechanistic insights into the formation of such novel hybrid composites.

关键词： Hybrid composite Coordination bond Albumin Fatty acid Porous layer Corrosion Theoretical approach

Effect of Deformation Temperature on Microstructure and Mechanical Properties of AZ31 Mg Alloy Processed by Differential-Speed Rolling

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Journal of Materials Science & Technology 2015年第5期31卷 498-503页

作者： Mosab Kaseem Bong kwon Chung hae woong Yang Kotiba Hamad Young Gun Ko School of Materials Science and Engineering Yeungnam University

A differential-speed rolling(DSR) was applied to AZ31 magnesium alloy sample at different rolling temperatures of 473,523,573,and 623 K with 1-pass and 2-pass *** microstructural evolution and mechanical properties of the deformed samples were *** rolling temperature was found to be an important parameter affecting the microstructural *** DSR at 473 K,the microstructure was more homogeneous than that obtained after deformation by equal-speed rolling(ESR).The fully recrystallized microstructures were generated after DSR at 573 and 623 *** to mechanical properties,the yield strength(YS) and ultimate tensile strength(UTS) decreased monotonously with increasing rolling *** contrast,the elongation of the DSR-deformed samples was improved as the rolling temperature *** strain hardening exponent(n) calculated by Hollomon equation increased with increasing the rolling temperature,which would explain an increase in the uniform elongation.

关键词： Differential-speed rolling Magnesium alloy Mechani

Effect of Squeeze Cast Process Parameters on Fluidity of Hypereutectic Al-Si Alloy

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Journal of Materials Science & Technology 2008年第1期24卷 7-11页

作者： Jong-Kyu Baek hae-Wook kwon School of Materials Science and Engineering Yeungnam University Gyeongsan 712-749 Korea

The effects of processing variables on the fluidity of hypereutectic Al-Si alloy melt during squeeze casting were *** maximum fluidity of Al-16.0%Si alloy during squeeze casting was obtained under the applied pressure of 30 *** fluidity increased with *** fluidity increased with silicon content in the range from 12.0% to 20.0%.That was decreased respectively by eutectic modification and primary silicon refinement.

关键词： Squeeze casting Al-alloy Fluidity Melt treatment

Tyrosine-mediated analog resistive switching for artificial neural networks

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Nano Research 2023年第1期16卷 858-864页

作者： Min-Kyu Song Seok Daniel Namgung Hojung Lee Jeong Hyun Yoon Young-woong Song Kang Hee Cho Yoon-Sik Lee Jong-Seok Lee Ki Tae Nam Jang-Yeon kwon School of Integrated Technology Yonsei UniversityIncheon 21983Republic of Korea Department of Mechanical Engineering Massachusetts Institute of TechnologyMA 02139USA Research Laboratory of Electronics Massachusetts Institute of TechnologyMA 02139USA Department of Materials Science and Engineering Seoul National UniversitySeoul 08826Republic of Korea Soft Foundry Seoul National UniversitySeoul 08826Republic of Korea School of Chemical and Biological Engineering Seoul National UniversitySeoul 08826Republic of Korea

The fourth industrial revolution indispensably brings explosive data processing and storage;thus,a new computing paradigm based on artificial intelligence-enabling device structure is urgently *** have received considerable attention in this regard because of their ability to process and store data at the same ***,fundamental problems with abrupt switching characteristics limit their practical *** address this problem,we utilized the concept of metaplasticity inspired by biosystems and observed gradual switching in the peptide-based memristor at high proton *** unexpectedly high slope value>1.7 in the logI–V curve at low voltage(≤400 mV)was considered the main origin,and it might arise from the modulatory response of proton ions on the threshold of Ag ion migration in the peptide *** the obtained gradual switching property at high proton conductivity,the device showed significantly increased accuracy of image recognition(~82.5%).We believe that such a demonstration not only contributes to the practical application of neuromorphic devices but also expands the bioinspired functional synthetic platform.

关键词： artificial synapse neuromorphic computing proton conductor peptide materials artificial neural network

Humidity-induced synaptic plasticity of ZnO artificial synapses using peptide insulator for neuromorphic computing

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Journal of Materials Science & Technology 2022年第24期119卷 150-155页

作者： Min-Kyu Song Hojung Lee Jeong Hyun Yoon Young-woong Song Seok Daniel Namgung Taehoon Sung Yoon-Sik Lee Jong-Seok Lee Ki Tae Nam Jang-Yeon kwon School of Integrated Technology Yonsei UniversityIncheon 21983South Korea Department of Materials Science and Engineering Seoul National UniversitySeoul 08826South Korea Soft Foundry Seoul National UniversitySeoul 08826South Korea School of Chemical and Biological Engineering Seoul National UniversitySeoul 08826South Korea

Neuromorphic devices inspired by the human brain have attracted significant attention because of their excellent ability for cognitive and parallel *** study presents ZnO-based artificial synapses with peptide insulators for the electrical emulation of biological *** demonstrated the dynamic responses of the device under various environmental *** proton-conducting property of the tyrosine-rich peptide enables time-dependent responses under ambient conditions such that various aspects of synaptic behaviors are emulated by the *** transition from short-term memory to longterm memory is achieved via electrochemical doping of ZnO by ***,we demonstrate an image classification simulation using a multi-layer perceptron model to evaluate the potential of the device for use in neuromorphic *** neural network based on our device achieved a recognition accuracy of 87.47% for the MNIST handwritten digit *** work proposes a novel device platform inspired by biosystems for brain-mimetic hardware systems.

关键词： Artificial synapse Neuromorphic computing Oxide semiconductor Proton conductor Artificial neural network

Delivery of nitric oxide-releasing silica nanoparticles for in vivo revascularization and functional recovery after acute peripheral nerve crush injury

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Neural Regeneration Research 2022年第9期17卷 2043-2049页

作者： Jung Il Lee Ji Hun Park Yeong-Rim Kim Kihak Gwon hae Won Hwang Gayoung Jung Joo-Yup Lee Jeong-Yun Sun Jong woong Park Jae Ho Shin Myoung-Ryul Ok Department of Orthopedic Surgery College of MedicineKorea UniversitySeoulRepublic of Korea Medical Sensor Biomaterial Research Institute Kwangwoon UniversitySeoulRepublic of Korea Center for Biomaterials Korea Institute of Science&TechnologySeoulRepublic of Korea Department of Materials Science and Engineering Seoul National UniversitySeoulRepublic of Korea Department of Orthopedic Surgery College of MedicineCatholic UniversitySeoulRepublic of Korea Department of Chemistry Kwangwoon UniversitySeoulRepublic of Korea

Nitric oxide(NO)has been shown to promote revascularization and nerve regeneration after peripheral nerve ***,in vivo application of NO remains challenging due to the lack of stable carrier materials capable of storing large amounts of NO molecules and releasing them on a clinically meaningful time ***,a silica nanoparticle system capable of reversible NO storage and release at a controlled and sustained rate was *** this study,NO-releasing silica nanoparticles(NO-SNs)were delivered to the peripheral nerves in rats after acute crush injury,mixed with natural hydrogel,to ensure the effective application of NO to the *** using a polymer dye and immunohistochemical staining for the detection of CD34(a marker for revascularization)results showed that NO-releasing silica nanoparticles increased revascularization at the crush site of the sciatic *** sciatic functional index revealed that there was a significant improvement in sciatic nerve function in NO-treated *** and anatomical analyses showed that the number of myelinated axons in the crushed sciatic nerve and wet muscle weight excised from NO-treated rats were ***,muscle function recovery was improved in rats treated with *** together,our results suggest that NO delivered to the injured sciatic nerve triggers enhanced revascularization at the lesion in the early phase after crushing injury,thereby promoting axonal regeneration and improving functional recovery.

关键词： crush injury nerve injury,nerve regeneration nitric oxide peripheral nerve revascularization silica nanoparticles