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Journal of Materials Science & Technology 2022年第22期117卷 8-22页

作者： Young-Kyun Kim kee-Ahn Lee Department of Materials Science and Engineering Inha UniversityIncheon 22212Republic of Korea Korea Institute of Materials Science(KIMS) Changwon 51508Republic of Korea

High-entropy alloys(HEAs)with interstitial atoms that are produced by additive manufacturing have gained intensive interest in the materials science community because of their suitability for constructing high-strength net-shape ***,a strategy to additionally enhance the strength of selective laser melted carbon-containing HEAs was *** as-built carbon-containing HEAs(C_(x)(Cr_(20)Mn_(20)Fe_(20)Co_(20)Ni_(20))_(100-x)(x=0.5 at.%,1.0 at.%,and 1.5 at.%))contain supersaturated carbon,and the extent of supersaturation increases as the carbon content *** subjected to aging treatment at 650°C for 1 h,the microstructure of the three alloys did not change at the grain ***,the microstructure at the sub-grain scale changed markedly,and these changes influenced the tensile properties and deformation *** particular,the tensile strength of aged 1.5C-HEA at 650°C was∼1.2 GPa at room temperature,which is higher than those reported for CrMnFeCoNi ***,the main deformation mechanism changed from deformation twinning to dislocation-mediated slip,resulting in much higher strain hardening capacity after the aging *** work led to the development of an alternative promising method that involves tailoring the microstructure,to enhance the mechanical properties of additively manufactured metallic materials that contain interstitial atoms.

关键词： Selective laser melting High-entropy alloy Carbon contents Aging Microstructure evolution Tensile property Deformation mechanism

Effect of carrier gas species on the microstructure and compressive deformation behaviors of ultra-strong pure copper manufactured by cold spray additive manufacturing

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Journal of Materials Science & Technology 2022年第2期97卷 264-271页

作者： Young-Kyun Kim kee-Ahn Lee Department of Materials Science and Engineering Inha UniversityIncheon 22212Republic of Korea

Cold spray(CS)which has recently become a promising additive manufacturing(AM)technology,was used to fabricate ultra-strong pure *** addition,the effects of carrier gas species on the microstructural characteristics,mechanical properties and deformation mechanisms were systemically *** CSAM copper manufactured with N_(2) carrier gas reveals a heterogeneous bimodal microstructure consisting of ultra-fine grains at the particle interface and relatively coarse grains in inner *** He carrier gas,a homogeneous grain structure consisting of ultra-fine grains in most areas was *** tests showed that N_(2) and He carrier gasses enabled ultra-high yield strengths of 340 and415 MPa,*** values are comparable to severely plastic deformed copper,which has extremely low ductility and shape *** the other hand,both samples showed a strain-softening phenomenon that does not commonly occur at room *** deformation microstructures revealed that dynamic recovery(DRV)and dynamic recrystallization(DRX)phenomena were generated despite being deformed at room *** on the above findings,the overall deformation mechanisms according to the carrier gas species in the CSAM copper manufacturing process were ***,the work hardening and softening behaviors of CSAM Cu are predicted by using a constitutive equation.

关键词： Cold spray additive manufacturing Carrier gas Pure Cu Mechanical properties Deformation behavior

Effect of asymmetrical channel chirping on field intensity patterns of supermodes and modal discrimination in index guided laser arrays

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Journal of Central South University 2014年第9期21卷 3513-3517页

作者： kee-Young Kwon College of Engineering Kongju National University

The effect of channel-width chirping on near- and far-field intensity patterns of the six supermodes was investigated. The supermode discrimination was evaluated in various channel-chirped index guided laser arrays. The results show that the linearly channel-chirped laser array has very good supermode discrimination which is better than that of a uniform laser array, the V channel-chirped laser array has the smallest radiation angle of the fundamental supermode among the calculated arrays, and the asymmetrically V channel-chirped array has a very small radiation angle of the fundamental supermode, which is smaller than that of the uniform array and also allows for very good fundamental supermode discrimination against the higher-order supermodes, which is better than that of the V channel-chirped laser array.

关键词： laser array channel-width chirping field pattern modal gain

Insights into female germ cell biology： from in vivo development to in vitro derivations

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Asian Journal of Andrology 2015年第3期17卷 415-420页

作者： Dajung Jung Kehkooi kee Department of Basic Medical Sciences Center for Stem Cell Biology and Regenerative Medicine School of Medicine Tsinghua University Beijing 100084 China

Understanding the mechanisms of human germ cell biology is important for developing infertility treatments. However, little is known about the mechanisms that regulate human gametogenesis due to the difficulties in collecting samples, especially germ cells during fetal development. In contrast to the mitotic arrest of spermatogonia stem cells in the fetal testis, female germ cells proceed into meiosis and began folliculogenesis in fetal ovaries. Regulations of these developmental events, including the initiation of meiosis and the endowment of primordial follicles, remain an enigma. Studying the molecular mechanisms of female germ cell biology in the human ovary has been mostly limited to spatiotemporal characterizations of genes or proteins. Recent efforts in utilizing in vitro differentiation system of stem cells to derive germ cells have allowed researchers to begin studying molecular mechanisms during human germ cell development. Meanwhile, the possibility of isolating female germline stem cells in adult ovaries also excites researchers and generates many debates. This review will mainly focus on presenting and discussing recent in vivo and in vitro studies on female germ cell biology in human. The topics will highlight the progress made in understanding the three main stages of germ cell developments： namely, primordial germ cell formation, meiotic initiation, and folliculogenesis.

关键词： embryonic stem cell female germline stem cell folliculogenesis in vitro derivations meiotic initiation primordial germ cell

Exotic structures arising from fake projective planes

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Science China Mathematics 2013年第1期56卷 43-54页

作者： yeUNG Sai-kee Department of Mathematics Purdue University

We present examples of exotic structures on pPC2#qPC2 for some small p and q obtained naturally from quotients of fake projective planes in complex geometry,which are classified by the work of Prasad-yeung and Cartwri... 详细信息

关键词： exotic four-folds fake projective planes

Extensions of 2-Homogeneous Polynomials on c_0

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Acta Mathematica Sinica,English Series 2008年第5期24卷 877-880页

作者： Pi-kee LIN Department of Mathematics University of MemphisMemphis TNUSA 38152

We prove that every 2-homogeneous polynomial on the complex co has a unique normpreserving extension to its bidual l∞.

关键词： Hahn-Banach extension homogeneous polynomial

Ordered SnO nanoparticles in MWCNT as a functional host material for high-rate lithium-sulfur battery cathode

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Nano Research 2017年第6期10卷 2083-2095页

作者： A-Young Kim Min Kyu Kim ji Young Kim Yuren Wen Lin Gu Van-Duong Dao Ho-Suk Choi Dongjin Byun Joong kee Lee Center for Energy Convergence Korea Institute of Science and Technology Seoul02792 Republic of Korea Department of Material Science and Engineering Korea University Seoul 02841 Republic of Korea Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China Department of Chemical Engineering & Applied Chemistry Chungnam National University Daejeon 34134 Republic of Korea

Lithium-sulfur battery has become one of the most promising candidates for next generation batteries, and it is still restricted due to the low sulfur conductivity, large volume expansion and severe polysulfide shuttling. Herein, we present a novel hybrid electrode with a ternary nanomaterial based on sulfur-impregnated multiwalled carbon nanotubes filled with ordered tin-monoxide nanoparticles （MWCNT-SnO/S）. Using a dry plasma reduction method, a mechanically robust material is prepared as a cathode host material for lithium-sulfur batteries. The MWCNT-SnO/S electrode exhibits high conductivity, good ability to capture polysulfides, and small volume change during a repeated charge-discharge process. In situ transmission electron microscopy and ultraviolet-visible absorption results indicate that the MWCNT-SnO host efficiently suppresses volume expansion during lithiation and reduces polysulfide dissolution into the electrolyte. Furthermore, the ordered SnO nanoparticles in the MWCNTs facilitate fast ion/electron transfer during the redox reactions by acting as connective links between the walls of the MWCNTs. The MWCNT-SnO/S cathode with a high sulfur content of 70 wt.% exhibits an initial discharge capacity of 1,682.4 mAh·g^-1 at 167.5 m·g^-1 （0.1 C rate） and retains a capacity of 530.1 mAh·g^-1 at 0.5 C after 1,000 cycles with nearly 100% Coulombic efficiency. Furthermore, the electrode exhibits the high capacity even at a high current rate of 20 C.

关键词： hybrid nanomaterial multiwalled carbonnanotube (MWCNT) ordered tin monoxide cathode high loading lithium-sulfur battery

Addendum to:Exotic structures arising from fake projective planes(Sci China Math,2013,56:43-54)

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Science China Mathematics 2015年第11期58卷 2473-2476页

作者： yeUNG Sai-kee Department of Mathematics Purdue University

The goal of this addendum is to generalize the argument of the original article [5] to handle the case of Cartwright-Steger surface, and to correct misprints in the tables in [5].

关键词：射影平面数学科学中国结构表面

Numerical Analysis of Secondary Cooling in Continuous Slab Casting

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Journal of Materials Science & Technology 2008年第3期24卷 389-390页

作者： kee-Hyeon Cho Byung-Moon Kim Research Institute of Industrial Science & Technology GyeongBuk Regional Stragetic Agency for Innovation

In the present study, a numerical optimization program has been developed for predicting the optimal secondary cooling patterns in a continuous slab caster. Optimization strategy using Broydon-Fletcher-Goldfarb-Shanno （13FGS） method is carried out by determining the constant heat transfer coefficients in each spray zone, which could satisfy the casting conditions and metallurgical criteria specified by the engineer. From the present results, it is found that even a slight variation in the pouring temperature, allowable surface temperature, and casting speed could give rise to the changes in the cooling pattern throughout the spray zones.

关键词： Continuous casting Secondary cooling Optimization

Electron-beam lithography for polymer bioMEMS with submicron features

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Microsystems & Nanoengineering 2016年第1期2卷 45-51页

作者： kee Scholten Ellis Meng Department of Biomedical Engineering University of Southern CaliforniaLos AngelesCA 90089-1111USA

We present a method for submicron fabrication of flexible,thin-film structures fully encapsulated in biocompatible polymer poly(chloro-p-xylylene)(Parylene C)that improves feature size and resolution by an order of magnitude compared with prior *** achieved critical dimensions as small as 250 nm by adapting electron beam lithography for use on vapor deposited Parylene-coated substrates and fabricated encapsulated metal structures,including conducting traces,serpentine resistors,and nano-patterned *** were probed electrically and mechanically demonstrating robust performance even under flexion or *** developed fabrication process for electron beam lithography on Parylene-coated substrates and characterization of the resulting structures are presented in addition to a discussion of the challenges of applying electron beam lithography to *** an application of the technique,a Parylene-based neural probe prototype was fabricated with 32 recording sites patterned along a 2 mm long shank,an electrode density surpassing any prior polymer probe.

关键词： electron beam lithography flexible electronics parylene C polymer MEMS