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Formability improvement and blank shape definition for deep drawing of cylindrical cup with complex curve profile from SPCC sheets using FEM

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Journal of Central South University 2014年第1期21卷 27-34页

作者： Duc-Toan Nguyen Duy-Khoe Dinh Hong-Minh Thi Nguyen Tien-Long Banh young-suk kim School of Mechanical Engineering Hanoi University of Science and Technology1A-Dai Co Viet StreetHai Ba Trung DistrictHanoi CityVietnam Department of Mechanical Engineering Hungyen University of Technology and EducationHungyenVietnam Department of Mechanical Engineering Kyungpook National University1370 SangyeokBuk-kuDaegu 702-701Korea

In the current work, to predict and improve the formability of deep drawing process for steel plate cold rolled commercial grade （SPCC） sheets, three parameters including the blanking force, the die and punch comer radius were considered. The experimental plan according to Taguchi＇s orthogonal array was coupled with the finite element method （FEM） simulations. Firstly, the data from the test of stress-strain and forming limit curves were used as input into ABAQUS/Explicit finite element code to predict the failure occurrence of deep drawing process. The three parameters were then validated to establish their effects on the press formability. The optimum case found via simulation was finally confirmed through an experiment. In order to obtain the complex curve profile of cup shape after deep drawing, the anisotropic behavior of earring phenomenon was modeled and implemented into FEM. After such phenomenon was correctly predicted, an error metric compared with design curve was then measured.

关键词： finite element method SPCC deep-drawing forming limit diagram criterion Taguchi's method earring prediction

Berberine inhibits inflammatory activation of rat brain microglia

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Neural Regeneration Research 2010年第18期5卷 1384-1390页

作者： Kyong Nyon Nam Jae-Hong kim Hoon-Ji Jung Jung-Mi Park Sang-Kwan Moon young-suk kim Sun Yeou kim Eunjoo H. Lee Department of Medical Science Graduate School of East-West Medical ScienceKyung Hee University Department of Cardiovascular & Neurologic Diseases (Stroke Center) Hospital of Oriental MedicineKyung Hee University

Chronic activation of microglial cells endangers neuronal survival through the release of various proinflammatory and neurotoxic factors. Berberine, the effective ingredient of Coptidis Rhizoma and Cortex Phellodendti, has a wide range of pharmacological functions, including anti-inflammatory, anti-atherosclerotic and anti-cancer effects. The neuroprotective potential of berberine has previously been demonstrated. The present study aimed to examine whether berberine could repress microglial activation and can be considered a potential therapeutic candidate to target neurodegenerative diseases. Primary microglial cells and BV2 microglial cells were cultured and stimulated with bacterial lipopolysaccharide （LPS）. Berberine chloride was treated prior to LPS or simultaneously with LPS stimulation. Results revealed that berberine was effective at inhibiting nitric oxide release from primary microglial cells when cells were exposed to the compound prior to LPS or simultaneously with LPS. It also reduced the LPS-stimulated production of tumor necrosis factor-α, interleukin-1β, prostaglandin E2, and intracellular reactive oxygen species and nuclear factor-kappa activation. Additionally, berberine reduced nitric oxide release from microglia stimulated with interferon-γ and amyloid β. These results suggest that berberine provides neuroprotection by reducing the production of various neurotoxic molecules from activated microglia.

关键词： brain inflammation berberine interleukin-1β microglia nuclear factor-kappa nitric oxide prostaglandin tumor necrosis factor-a

Prediction of forming limit curve for pure titanium sheet

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Transactions of Nonferrous Metals Society of China 2018年第2期28卷 319-327页

作者： young-suk kim Bong-Hyun LEE Seung-Han YANG School of Mechanical Engineering Kyungpook National University Daegu-Gyeongbuk Center Korea Automotive Technology Institute

Commercially pure titanium（CP Ti） has been actively used in the plate heat exchanger due to its light weight, high specific strength, and excellent corrosion resistance. However, researches for the plastic deformation characteristics and press formability of the CP Ti sheet are not much in comparison with automotive steels and aluminum alloys. The mechanical properties and hardening behavior evaluated in stress-strain relation of the CP Ti sheet are clarified in relation with press formability. The flow curve denoting true stress-true strain relation for CP Ti sheet is fitted well by the kim-Tuan hardening equation rather than Voce and Swift models. The forming limit curve（FLC） of CP Ti sheet as a criterion for press formability was experimentally evaluated by punch stretching test and analytically predicted via Hora＇s modified maximum force criterion. The predicted FLC by adopting kim-Tuan hardening model and appropriate yield function shows good correlation with the experimental results of punch stretching test.

关键词： kim-Tuan hardening equation Hora modified maximum force criterion pure titanium sheet forming limit curve

Flexible thermocouple using a thermoelectric graphene fiber with a seamless junction

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Journal of Materials Science & Technology 2024年第5期172卷 15-22页

作者： Seungwon kim Soomook Lim Myeong Hee Jeong Wonjoon kim Seunghyun Baik Ji Won suk School of Mechanical Engineering Sungkyunkwan UniversitySuwonGyeonggi-do 16419Republic of Korea Department of Smart Fab.Technology Sungkyunkwan UniversitySuwonGyeonggi-do 16419Republic of Korea SKKU Advanced Institute of Nanotechnology(SAINT) Sungkyunkwan UniversitySuwonGyeonggi-do 16419Republic of Korea

Temperature is an important physical variable that indicates the condition of the human body and artificial *** wearable applications require the development of temperature sensors with different form *** this study,a fiber-shaped thermoelectric temperature sensor is fabricated using a continuous graphene fiber whose two halves possess different reduction states.A seamless junction is formed by partially reducing a wet-spun graphene oxide fiber with hydroiodic acid(HI)solutions of different ***-half of the fiber is mildly reduced with 0.97 wt%HI,while the other half is highly reduced with 30.6 wt%*** different reduction states of the graphene composite fiber result in different Seebeck coefficients,allowing for the fabrication of a fiber-shaped graphene thermocou-ple without any laborious *** flexible graphene thermocouple exhibits high sensitivity with a thermopower of 12.5μV K^(-1)in the temperature range of room temperature to∼70℃.Furthermore,it exhibits high linearity with a correlation coefficient exceeding 0.995 and fast response with a time constant of 0.24 *** to its mechanical robustness and flexibility,the stand-alone graphene ther-mocouple can be knitted into a cotton fabric glove,which presents a fast response to environmental changes without any external power *** work offers a unique fabrication method for producing a high-performance,flexible thermocouple that features a seamless and clear junction without the use of additional *** alternative method eliminates the complicated assembly processes typically required for conventional thermocouples.

关键词： Graphene fiber Thermocouple Reduced graphene oxide Flexible temperature sensor Seebeck coefficient

Retinal artery/arteriole occlusion risks after endovascular treatment for unruptured intracranial aneurysm

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Stroke & Vascular Neurology 2024年第3期9卷 295-305,I0251-I0263页

作者： Hae Rang kim Min Jeoung kim Sunyeup kim Myung Soo Chang Dong Joon kim Byung Moon kim Keun young Park Yong Bae kim Christopher Seungkyu Lee suk Ho Byeon Sung Soo kim Seung Won Lee Yong Joon kim Department of Ophthalmology CHA Bundang Medical CenterCHA University College of MedicineSeongnamKorea(the Republic of) Department of Neurosurgery Severance Stroke CenterSeverance HospitalYonsei University College of MedicineSeoulKorea(the Republic of) Department of Neurosurgery Uijeongbu St.Mary’s HospitalThe Catholic University of Korea College of MedicineUijeongbuKorea(the Republic of) Department of Medical AI Sungkyunkwan University School of MedicineSuwonKorea(the Republic of) Department of Ophthalmology Institute of Vision ResearchYonsei University College of MedicineSeoulKorea(the Republic of) Department of Radiology Severance Stroke CenterSeverance HospitalYonsei University College of MedicineSeoulKorea(the Republic of) Department of Precision Medicine Sungkyunkwan University School of MedicineSuwonKorea(the Republic of)

Background To evaluate the association between retinal artery/arteriole occlusion(RAO)and unruptured intracranial aneurysm(UIA).Methods Incident UIA patients from a nationwide cohort(n=253240)were categorised into three groups based on subsequent treatment:observation(n=208993),microsurgical clipping(n=14168)and endovascular treatment(EVT)groups(n=30079).The incidence and the incident time of RAO were *** of RAO and associated risk factors were ***,a hospital cohort comprising 2569 consecutive UIA patients treated at a tertiary hospital was analysed with detailed clinical information of *** In the nationwide cohort analysis,the incidence of RAO was significantly higher in EVT group than in observation and clipping groups,especially within 60 days(early RAO(within 60 days):HR=4.00,95%CI:2.44 to 6.56);delayed RAO(after 60 days:HR=1.74,95%CI:1.13 to 2.68).Multivariable analysis showed that the presence of chronic kidney disease(p=0.009)and use of a balloon microcatheter during the procedure(p=0.013)were associated with a higher risk of *** hospital cohort analysis,11(0.8%)cases of RAO occurred after EVT,whereas none occurred after microsurgical clipping(pyounger and received balloon microcatheters more frequently than their *** cases of RAO(90.9%)occurred in paraclinoid aneurysms,where EVT was preferred over microsurgical *** Performing EVT for UIA may increase the risk of subsequent *** should be taken when treating paraclinoid aneurysms with balloon microcatheters.

关键词： treatment nationwide balloon

Efficacy of chemotherapy containing bevacizumab in patients with metastatic colorectal cancer according to programmed cell death ligand 1

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World Journal of Gastrointestinal Oncology 2024年第8期16卷 3521-3528页

作者： Shin Woo Kang Sung Hee Lim Min-Ji kim Jeeyun Lee young suk Park Ho Yeong Lim Won Ki Kang Seung Tae kim Division of Hematology Oncology Department of MedicineSamsung Medical CenterSungkyunkwan University School of MedicineSeoul 06351South Korea Samsung Biomedical Research Institute Samsung Medical CenterSeoul 06351South Korea

BACKGROUND Bevacizumab,an anti-vascular endothelial growth factor(VEGF)monoclonal antibody,inhibits angiogenesis and reduces tumor *** VEGF-C,lactate dehydrogenase,and inflammatory markers have been reported as predictive markers related to bevacizumab *** cell death ligand 1(PD-L1)could act upon VEGF receptor 2 to induce cancer cell angiogenesis and *** To investigate the efficacy of bevacizumab-containing chemotherapy in patients with metastatic colorectal cancer(CRC)according to the expression of *** This analysis included CRC patients who received bevacizumab plus FOLFOX or FOLFIRI as first-line therapy between June 24,2014 and February 28,2022,at Samsung Medical Center(Seoul,South Korea).Analysis of patient data included evaluation of PD-L1 expression by the combined positive score(CPS).We analyzed the efficacy of bevacizumab according to PD-L1 expression status in patients with *** A total of 124 patients was included in this *** all patients were treated with bevacizumab plus FOLFIRI or FOLFOX as the first-line *** 77%of patients received FOLFOX,23%received FOLFIRI as backbone first-line *** numbers of patients with a PD-L1 CPS of 1 or more,5 or more,or 10 or more were 105(85%),64(52%),and 32(26%),*** results showed no significant difference in progression-free survival(PFS)and overall survival(OS)with bevacizumab treatment between patients with PDL1 CPS less than 1 and those with PD-L1 CPS of 1 or more(PD-L1<1%vs PD-L1≥1%;PFS:P=0.93,OS:P=0.33),between patients with PD-L1 CPS less than 5 and of 5 or more(PD-L1<5%vs PD-L1≥5%;PFS:P=0.409,OS:P=0.746),and between patients with PD-L1 CPS less than 10 and of 10 or more(PD-L1<10%vs PD-L1≥10%;PFS:P=0.529,OS:P=0.568).CONCLUSION Chemotherapy containing bevacizumab can be considered as first-line therapy in metastatic CRC irrespective of PD-L1 expression.

关键词： Bevacizumab Colorectal cancer Programmed cell death ligand 1 expression First-line chemotherapy Metastatic colorectal cancer

Micromechanics on Spherical Contact with Roughness

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Micromechanics on Spherical Contact with Roughness

Integration of earth-abundant cocatalysts for high-performance photoelectrochemical energy conversion

亚洲精密工程、微纳技术国际会议

作者： Jae Sung Jeon Sangil Hyun young-suk kim School of Mechanical Engineering Kyungpook National University Taegu 702-701 South Korea School of Mechanical Engineering Kyungpook National University Taegu 702-701 South Korea School of Mechanical Engineering Kyungpook National University Taegu 702-701 South Korea

Finite-element methods are used to study non-adhesive, frictionless rough contact of elastic and plastic solids. Roughness on spherical surfaces is realized by self-affine fractal. True contact area between the rough surfaces and flat rigid surfaces increases with power law under external normal loads. The power exponent is sensitive to surface roughness as well as the curvature of spherical geometry. Surface contact pressures are analyzed and compared for the elastic and plastic solids. Distributions of local contact pressure are shown dependent on the surface roughness and the yield stress of plastic solids.

关键词： finite element method, nano-contacts, self-affine fractal surface.

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Journal of Energy Chemistry 2024年第1期88卷 336-355,I0008页

作者： Joonhee Ma Sang Hyun Ahn Soo young kim Department of Materials Science and Engineering Korea UniversitySeoul 02841Republic of Korea School of Chemical Engineering and Materials Science Chung-Ang University84 Heukseok-roDongjak-guSeoul 06974Republic of Korea

Photoelectrochemical(PEC)energy conversion has emerged as a promising and efficient approach to sustainable energy harvesting and *** utilizing semiconductor photoelectrodes,PEC devices can harness solar energy and drive electrochemical reactions such as water splitting or carbon dioxide(CO_(2))reduction to generate clean fuels and value-added ***,PEC energy conversion faces several challenges such as high overpotential,sluggish reaction kinetics,charge carrier recombination,and stability issues,which limit its practical ***,significant research has been conducted to improve the overall conversion efficiency of PEC *** particularly promising approach is the use of cocatalysts,which involves introducing specific cocatalysts onto the photoelectrode surface to promote charge separation,improve reaction kinetics,and reduce the overpotential,thereby enhancing the overall performance of PEC energy *** review provides a comprehensive overview of the recent developments in the earth-abundant cocatalysts for PEC water splitting and CO_(2) *** main earth-abundant catalysts for the PEC water splitting include transition-metal dichalcogenide(TMD)-based materials,metal phosphides/carbides,and metal oxides/***,PEC-CO_(2)RR was divided into C_(1) and C_(2+)based on the final product since various products could be produced,focusing on diverse earth-abundant materials-based *** addition,we provide and highlight key advancements achieved in the very recent reports on novel PEC system design engineering with ***,the current problems associated with PEC systems are discussed along with a suggested direction to overcome these obstacles.

关键词： Solar energy Photo-electrochemical Water splitting CO_(2)reduction Cocatalysts

Tailoring Classical Conditioning Behavior in TiO_(2) Nanowires:ZnO QDs-Based Optoelectronic Memristors for Neuromorphic Hardware

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Nano-Micro Letters 2024年第7期16卷 265-280页

作者： Wenxiao Wang Yaqi Wang Feifei Yin Hongsen Niu young-Kee Shin Yang Li Eun-Seong kim Nam-young kim School of Information Science and Engineering University of JinanJinan 250022People’s Republic of China RFIC Centre NDAC CentreKwangwoon UniversityNowon-guSeoul 139-701South Korea Department of Electronics Engineering Kwangwoon UniversityNowon-GuSeoul 139-701South Korea School of Microelectronics Shandong UniversityJinan 250101People’s Republic of China Department of Molecular Medicine and Biopharmaceutical Sciences Seoul National UniversitySeoul 08826South Korea

Neuromorphic hardware equipped with associative learn-ing capabilities presents fascinating applications in the next generation of artificial ***,research into synaptic devices exhibiting complex associative learning behaviors is still ***,an optoelec-tronic memristor based on Ag/TiO_(2) Nanowires:ZnO Quantum dots/FTO was proposed and constructed to emulate the biological associative learning *** implementation of synaptic behaviors,including long and short-term plasticity,and learning-forgetting-relearning behaviors,were achieved in the device through the application of light and electrical *** the optoelectronic co-modulated characteristics,a simulation of neuromorphic computing was conducted,resulting in a handwriting digit recognition accuracy of 88.9%.Furthermore,a 3×7 memristor array was constructed,confirming its application in artificial visual *** importantly,complex biological associative learning behaviors were emulated by mapping the light and electrical stimuli into conditioned and unconditioned stimuli,*** training through associative pairs,reflexes could be triggered solely using light ***-sively,under specific optoelectronic signal applications,the four features of classical conditioning,namely acquisition,extinction,recovery,and generalization,were elegantly *** work provides an optoelectronic memristor with associative behavior capabilities,offering a pathway for advancing brain-machine interfaces,autonomous robots,and machine self-learning in the future.

关键词： Artificial intelligence Classical conditioning Neuromorphic computing Artificial visual memory Optoelectronic memristors ZnO Quantum dots