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Foliations associated to harmonic maps on some complex two ball quotients

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Science China Mathematics 2017年第6期60卷 1137-1148页

作者： YEUNG Sai-kee Department of Mathematics Purdue University West Lafayette IN 47907 USA

This article is an attempt to understand harmonic and holomorphic maps between two bounded symmetric domains in special situations. We study foliations associated to a lattice-equivariant harmonic map of small rank from a complex ball to another. The result is related to rigidity of some complex two ball *** open questions are raised as well.

关键词： harmonic maps foliations rigidity

Kinetic Study for Adsorption of Heavy Metals on Zeolite

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Journal of Harbin Institute of Technology(New Series) 2022年第1期29卷 70-76页

作者： Kow Jing Yang Lim Lee Fong chan Mieow kee Aseel Ali Saeed Centre for Water Research Faculty of EngineeringBuilt Environment and Information TechnologySEGi UniversityPetaling JayaSelangor 47810Malaysia

Heavy metals⁃polluted water has negative impact on the *** Malaysia,minimum discharge limit for Cu^(2+)and Zn^(2+)are 1 mg/L and 2 mg/L,*** is a highly porous adsorbent and its performance is affected by various factors,including contact time and ***,the objective of this study is to identify an ideal operating condition to treat Cu^(2+)and Zn^(2+)solutions up to the allowable discharge limit,by considering the pH and contact time *** kinetic models were studied to identify the adsorption mechanism of the heavy metal removal *** solute batch adsorption experiment was conducted within pH 3-11 from 30 to 150 *** showed that hydration enthalpy(ΔHhyd)governed the selectivity of heavy metals,where a maximum of 90.87%Zn^(2+)(ΔH_(hyd)=-1955 kJ/mol)and 82.15%Cu^(2+)(ΔH_(hyd)=-2010 kJ/mol)removals were found at pH≥*** pH adjustment,selectivity towards Cu^(2+)was higher compared with Zn^(2+)due to the size of hydration radii,where Cu^(2+)is 0.11Åsmaller than Zn^(2+).By considering both pH and contact time factors,this study shows that by adjusting the pH of Zn^(2+)solutions to a minimum pH value of 7,the contact time required to achieve maximum Zn^(2+)removal rate was 90%,which can be achieved within 60 ***,zeolite performed better in Cu^(2+)removal without any pH adjustment where a maximum of 94%was achieved at 120 *** concentration of 0.523 mg/L Cu^(2+)and 0.981 mg/L Zn^(2+)were obtained in this *** study showed that Ritchie’s equation predicted Cu^(2+)adsorption the best,while Zn^(2+)adsorption could be represented by Elovich *** suggested that the adsorption on the activate site governed Cu^(2+)and Zn^(2+)removal ***,future work should focus on modifying zeolite surface to improve the adsorptive performance.

关键词： zeolite heavy metal removal pH contact time

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Efficient Flexible M-Tree Bulk Loading Using FastMap and Space-Filling Curves

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Computers, Materials & Continua 2021年第2期66卷 1251-1267页

作者： Woong-kee Loh Department of Software Gachon UniversitySeongnam13120South Korea

Many database applications currently deal with objects in a metric *** of such objects include unstructured multimedia objects and points of interest(POIs)in a road *** M-tree is a dynamic index structure that facilitates an efficient search for objects in a metric *** have been conducted on the bulk loading of large datasets in an ***,because previous algorithms involve excessive distance computations and disk accesses,they perform poorly in terms of their index construction and search *** study proposes two efficient M-tree bulk loading *** algorithms minimize the number of distance computations and disk accesses using FastMap and a space-filling curve,thereby significantly improving the index construction and search *** second algorithm is an extension of the first,and it incorporates a partitioning clustering technique and flexible node architecture to further improve the search *** the use of various synthetic and real-world datasets,the experimental results demonstrated that our algorithms improved the index construction performance by up to three orders of magnitude and the search performance by up to 20.3 times over the previous algorithm.

关键词： M-tree metric space bulk loading FastMap space-filling curve

Stabilized sub-grain and nano carbides-driven 1.2 GPa grade ultra-strong CrMnFeCoNi high-entropy alloy additively manufactured by laser powder bed fusion

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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

Thermal pyrolysis conversion of methane to hydrogen(H_(2)):A review on process parameters,reaction kinetics and techno-economic analysis

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Chinese Chemical Letters 2024年第8期35卷 62-73页

作者： Yi Herng chan Zhe Phak chan Serene Sow Mun Lock Chung Loong Yiin Shin Ying Foong Mee kee Wong Muhammad Anwar Ishak Ven Chian Quek Shengbo Ge Su Shiung Lam PETRONAS Research Sdn.Bhd.(PRSB) Kawasan Institusi BangiLot 3288&3289Off Jalan Ayer ItamKajang 43000Malaysia PETRONAS Carbon Capture&Storage(CCS)Enterprise PETRONAS Twin TowersKuala Lumpur City CentreKuala Lumpur 50088Malaysia CO_(2)Research Center(CO2RES) Department of Chemical EngineeringUniversiti Teknologi PETRONASSeri Iskandar 32610Malaysia Department of Chemical Engineering and Energy Sustainability Faculty of EngineeringUniversiti Malaysia Sarawak(UNIMAS)Kota Samarahan 94300Malaysia Institute of Sustainable and Renewable Energy(ISuRE) Universiti Malaysia Sarawak(UNIMAS)Kota Samarahan 94300Malaysia Higher Institution Centre of Excellence(HICoE) Institute of Tropical Aquaculture and Fisheries(AKUATROP)Universiti Malaysia TerengganuKuala Nerus 21030Malaysia Co-Innovation Center of Efficient Processing and Utilization of Forest Resources College of Materials Science and EngineeringNanjing Forestry UniversityNanjing 210037China Center for Global Health Research(CGHR) Saveetha Medical CollegeSaveetha Institute of Medical and Technical Sciences(SIMATS)Saveetha UniversityChennai 602105India

Hydrogen(H_(2))is a promising renewable energy which finds wide applications as the world gears toward low-carbon ***,current H_(2) production via steam methane reforming of natural gas or gasification of coal are laden with high CO_(2) ***,methane(CH_(4))pyrolysis has emerged as a potential technology to generate low-carbon H_(2) and solid *** this review,the current state-of-art and recent progress of H_(2) production from CH_(4) pyrolysis are reviewed in *** such as funda-mental mechanism and chemistry involved,effect of process parameters on the conversion efficiency and reaction kinetics for various reaction media and catalysts are elucidated and critically ***-ature,among other factors,plays the most critical influence on the methane pyrolysis *** metal/salt could lower the operating temperature of methane pyrolysis to1000℃.Based on the reaction kinetics,metal-based cata-lysts were more efficient in lowering the activation energy of the reaction to 29.5-88 kJ/mol from that of uncatalyzed reaction(147-420.7 kJ/mol).Besides,the current techno-economic performance of the pro-cess reveals that the levelized cost of H_(2) is directly influenced by the sales price of carbon(by-product)generated,which could offset the overall ***,the main challenges of reactor design for efficient product separation and retrieval,as well as catalyst deactivation/poisoning need to be debottlenecked.

关键词： Pyrolysis Methane Hydrogen Reaction kinetics Techno-economic analysis

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