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Grain size dependence of flow stress in ECAPed Ti with constant texture

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中国有色金属学会会刊：英文版 2012年第S3期22卷 673-677页

作者： chang-Young hyun ho-Kyung KIM Department of Materials Science and Engineering Seoul National University of Science and Technology Department of Automotive Engineering Seoul National University of Science and Technology

The effect of grain size on the flow stress in an ECAPed Ti with a constant texture was investigated,assuming that 2,4,5 and 6 passes microstructures have a similar *** average size of recrystallized grains decreased to 0.5 μm,0.4 μm,and 0.3 μm with respect to the ECAP pass number of 2,4,and 6,*** ultimate tensile strength (UTS) and yield strength (YS) increase with an increase in the number of *** UTS and YS of the 6 passes ECAPed sample were found to be 740.2 MPa and 580.3 MPa,*** equation for the flow stress of an ECAPed Ti with a constant texture as a function of the strain and grain size was derived for the ECAPed *** following equation was finally obtained:σ(ε)=103.9+1825ε-9.6ε1/2·d-1/2+8.3d-1/2.

关键词： Ti mechanical properties grain size flow stress equal channel angular pressing

Optimal rotor wear design in hypotrochoidal gear pump using genetic algorithm

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Journal of Central South University 2011年第3期18卷 718-725页

作者： KWON Soon-man KIM chang-hyun SHIN Joong-ho Department of Mechanical Design and Manufacturing Engineering Changwon National University

The wear rate between the rotors of a hypotrochoidal gear pump is *** the knowledge of shape design on the rotors,the contact stresses without hydrodynamic effect between the rotor teeth were evaluated through the calculation of the Hertzian contact *** on the above results and the sliding velocity between the rotors,a genetic algorithm (GA) was used as an optimization technique forminimizing the wear rate proportional factor (WRPF).The result shows that the wear rate or the WRPF can be reduced considerably,*** 12.8%,throughout the optimization using GA.

关键词： gerotor hypotrochoidal gear pump Hertzian contact stress wear rate proportional factor genetic algorithm

Polygonal multi-polymorphed Li4Ti5Oi2@rutile TiO2 as anodes in lithium-ion batteries

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Nano Research 2019年第4期12卷 897-904页

作者： chang hyun Hwang Hee-eun Kim Inho Nam Jin ho Bang Department ofBionano Technology Hanyang University 55 Hanyangdaehak-ro Sangnok-gu Ansan Gyeonggi-do 15588 Republic of Korea School of Chemical Engineering & Materials Science Chung-Ang University 84 Heukseok-ro Dongjak-gu Seoul 06974 Republic of Korea Department of Chemical and Molecular Engineering Hanyang University 55 Hanyangdaehak-ro Sangnok-gu Ansan Gyeonggi-do 15588 Republic of Korea

Li4Ti50i2 (LTO) has attracted considerable attention in lithium-ion battery (LIB) applications because of its favorable characteristics as an anode material. Despite its promise, the widespread use of LTO is still limited primarily due to its intrinsically poor electric and ionic con ductivities and high surface reactivity. To address these issues, we desig ned polyg onal nano architectures composed of various Li-Ti oxide crystal polymorphs by a facile synthesis route. Depending on the pH condition, this synthesis approach yields multi-polymorphed Li-Ti oxides where the interior is dominantly composed of a Li-rich phase and the exterior is a Li-deficient (or Li-free) phase. As one of these variations, a polygonal LTO-rutile TiO2 structure is formed. The rutile TiO2 on the surface of this LTO composite significantly improves the kinetics of Li^+ insertion/extraction because the channel along the o-axis in TQ2 provides a Li^+ highway due to the significantly low energy barrier for Li^+ diffusion. Moreover, the presenee of rutile TiO2, which is less reactive with a carbonate-based electrolyte, ensures Iong-term stability by suppress)ng the undesirable interfacial reaction on LTO.

关键词： micro-polygon structure Li-Ti oxide multi-polymorphs Li4Ti5Oi2@ rutile TiO2 anode lithium-ion batteries

Comparative study on discharge conditions in micro-hole electrical discharge machining of tungsten carbide (WC-Co) material

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中国有色金属学会会刊：英文版 2009年第B09期19卷 114-118页

作者： hyun-Seok TAK chang-Seung HA Dong-hyun KIM ho-Jun LEE Hae-June LEE Myung-chang KANG National Core Research Center for Hybrid Materials Solution Pusan National University Department of Electrical Engineering Pusan National University

WC-Co is used widely in die and mold industries due to its unique combination of hardness, strength and wear-resistance. For machining difficult-to-cut materials, such as tungsten carbide, micro-electrical discharge machining(EDM) is one of the most effective methods for making holes because the hardness is not a dominant parameter in EDM. This paper describes the characteristics of the discharge conditions for micro-hole EDM of tungsten carbide with a WC grain size of 0.5 μm and Co content of 12%. The EDM process was conducted by varying the condenser and resistance values. A R-C discharge EDM device using arc erosion for micro-hole machining was suggested. Furthermore, the characteristics of the developed micro-EDM were analyzed in terms of the electro-optical observation using an oscilloscope and field emission scanning electron microscope.

关键词：电火花加工碳化钨钴难切削材料硬质合金放电扫描电子显微镜微孔模具行业

Prospects for nucleic acid-based therapeutics against hepatitis C virus

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World Journal of Gastroenterology 2013年第47期19卷 8949-8962页

作者： chang ho Lee Ji hyun Kim Seong-Wook Lee Department of Molecular Biology Institute of Nanosensor and BiotechnologyDankook UniversityYongin 448-701South Korea

In this review,we discuss recent advances in nucleic acid-based therapeutic technologies that target hepatitis C virus(HCV)*** the HCV genome is present exclusively in RNA form during replication,various nucleic acid-based therapeutic approaches targeting the HCV genome,such as ribozymes,aptamers,siRNAs,and antisense oligonucleotides,have been suggested as potential tools against *** acids are potentially immunogenic and typically require a delivery tool to be utilized as *** limitations have hampered the clinical development of nucleic acid-based ***,despite these limitations,nucleic acid-based therapeutics has clinical value due to their great specificity,easy and large-scale synthesis with chemical methods,and pharmaceutical ***,nucleic acid therapeutics are expected to broaden the range of targetable molecules essential for the HCV replication cycle,and therefore they may prove to be more effective than existing therapeutics,such as interferon-αand ribavirin combination *** review focuses on the current status and future prospects of ribozymes,aptamers,siRNAs,and antisense oligonucleotides as therapeutic reagents against HCV.

关键词： Hepatitis C virus Nucleic acid-based therapeutics Ribozyme Aptamer siRNA Antisense oligonucleotide

Memristive Devices Based on Two-Dimensional Transition Metal Chalcogenides for Neuromorphic Computing

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Nano-Micro Letters 2022年第4期14卷 29-58页

作者： Ki chang Kwon Ji hyun Baek Kootak hong Soo Young Kim ho Won Jang Department of Materials Science and Engineering Research Institute of Advanced MaterialsSeoul National UniversitySeoul 08826Republic of Korea Interdisciplinary Materials Measurement Institute Korea Research Institute of Standards and Science(KRISS)Daejeon 34133Republic of Korea Department of Materials Science and Engineering Institute of Green Manufacturing TechnologyKorea UniversitySeoul 02841Republic of Korea Advanced Institute of Convergence Technology Seoul National UniversitySuwon 16229Korea

Two-dimensional(2D)transition metal chalcogenides(TMC)and their heterostructures are appealing as building blocks in a wide range of electronic and optoelectronic devices,particularly futuristic memristive and synaptic devices for brain-inspired neuromorphic computing *** distinct properties such as high durability,electrical and optical tunability,clean surface,flexibility,and LEGO-staking capability enable simple fabrication with high integration density,energy-efficient operation,and high *** review provides a thorough examination of high-performance memristors based on 2D TMCs for neuromorphic computing applications,including the promise of 2D TMC materials and heterostructures,as well as the state-of-the-art demonstration of memristive *** challenges and future prospects for the development of these emerging materials and devices are also *** purpose of this review is to provide an outlook on the fabrication and characterization of neuromorphic memristors based on 2D TMCs.

关键词： Two-dimensional materials Memristors Neuromorphic computing Artificial synapses Transition metal chalcogenides

Dual cycloid gear mechanism for automobile safety pretensioners

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Journal of Central South University 2012年第2期19卷 365-373页

作者： SHIN Joong-ho KIM chang-hyun YUN Pyeong-hwa KWON Soon-man Department of Mechanical Design and Manufacturing Changwon National University

The most conventional vehicle pretensioner system consists of an internal gear pair with involute teeth. however, it has been well known that the corresponding gear pairs are relatively weak under the situation of impact loadings. To improve this phenomenon, a new pretensioning gear system with cycloid teeth rather than the involute ones was proposed, and dual cycloidal gear mechanisms were designed for satisfying geometric constraints and dynamic loading conditions. The simulations of the prototypes were conducted by LS-DYNA program and the experiments for a prototype were performed for a dynamic model with impact loading devices. The results show that the better operation and the smoother motion are confirmed in the proposed cycloidal gear system rather than the conventional one without interferences between gear teeth under the impact of a crash.

关键词： seat belt pretensioner internal gear pairs involute gear dual cycloid gear

Intramedullary spinal cord metastasis from pancreatic neuroendocrine tumor

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World Journal of Gastroenterology 2014年第38期20卷 14063-14067页

作者： Jung ho Kim chang Lim hyun Sang hoon Han Department of Internal Medicine Gachon University Gil Medical Center Department of Pathology Jeju National University School of Medicine Department of Internal Medicine Jeju National University School of Medicine

Intramedullary spinal cord metastasis(ISCM) is very rare and its optimal treatment remains controversial. Pancreatic neuroendocrine tumor(pNET) is a rare tumor that usually presents with hepatic metastasis. Hepatic failure due to tumor progression is the major cause of death in cases of pNET. To date,no report has described a case of ISCM from pNET. Although spinal cord metastasis of a solid tumor is uncommon,it is a critical condition that can cause a potentially irreversible loss of neurologic function. Here,we report the case of a 45-year-old man who presented with leg weakness and voiding difficulty,and was found to have ISCM from pNET. Surgical treatment prevented further neurological deterioration. This is the first case report of ISCM from pNET.

关键词： Intramedullary Spinal cord neoplasm Metastasis Neuroendocrine tumor Pancreas

Distribution of electric field for carbon nanotube assembly: Experiments (II)

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Transactions of Nonferrous Metals Society of China 2011年第A01期21卷 121-125页

作者： Soongeun KWON Soo-hyun KIM Kwang-ho KIM Myung-chang KANG hyung-woo LEE Department of Mechanical Engineering Korea Advanced Institute of Science and Technology (KAIST) Daejeon 305-701 Korea National Core Research Center for Hybrid Materials Solution Pusan National University

The distribution effect of electric field on the alignment and attachment of carbon nanotubes （CNTs） were investigated. The experimental results were compared with the simulation results according to three different shaped electrodes. In previous simulation, the round shaped electrodes were expected to be more effective for aligning and attaching a single CNT between two electrodes than conical or rectangular shaped electrodes. To verify the simulation results, three different shaped electrodes were introduced and a single multi-walled carbon nanotube （MWNT） was attached. The optimal conditions for aligning and attaching MWNTs such as the frequency, applied voltage and concentration of MWNTs solution were investigated. Through repeated experiments, frequency of 100 kHz-10 MHz, applied voltage of 0.3-1.3 V^s/~m, concentration of 5 ktg/mL in MWNTs solution were obtained as a possible condition range to attach MWNTs. Under these conditions, the yield of MWNTs attachment between two electrodes was up to 70%. In previous simulation, furthermore, it was verified that the size of the stable or quasi-stable region made CNTs aligned and attached on different shaped electrodes from the comparison of the experimental and simulation results. Most single MWNT attachment was accomplished on the round shaped electrodes.

关键词： carbon nanotubes dielectrophoresis round shaped electrode simulation