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Microstructure and properties of alumina-silicon carbide nanocomposites fabricated by pressureless sintering and post hot-isostatic pressing

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Transactions of Nonferrous Metals society of China 2011年第A01期21卷 1-6页

作者： young-Keun JEONG Koichi NIIHARA National Core Research Center for Hybrid Materials solution Pusan National University Nagaoka University of Technology

A1203/5%sIC nanocomposites were fabricated by pressureless sintering using MgO as a sintering aid and then post hot-isostatic pressed （HIP）, which can subsequently break through the disadvantage of hot-pressing process. The MgO additive was able to promote the densification of the composites, but could not induce the grain growth of A1203 matrix due to the grain growth inhibition by nano-sized siC particles. After HIP treatment, A12OJsiC nanocomposites achieved full densification and homogeneous distribution of nano-sized siC particles. Moreover, the fracture morphology of HIP treated specimens was identical with that of the hot-pressed A1203/siC nanocomposites showing complete transgranular fracture. Consequently, high fracture strength of 1 GPa was achieved for the A1203/5%sIC nanocomposites by pressureless sintering and post HIP process.

关键词： nanocomposite pressureless sintering fracture strength

Magnetoelectric multiferroicity and quantum paraelectricity in hexaferrites

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science China(Physics,Mechanics & Astronomy) 2019年第4期62卷 1-13页

作者： shi-Peng shen young sun Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences school of Physical sciences University of Chinese Academy of Sciences

Multiferroic materials with coexisting ferroelectric and magnetic orders have attracted tremendous research interests because of their intriguing fundamental physics as well as potential applications in the next-generation multifunctional devices. Hexaferrites with conical magnetic structures are among the most promising single-phase multiferroics because strong magnetoelectric effects can be achieved in them from low temperatures up to room temperature in low magnetic fields. In this review, after briefly introducing the background on multiferroics and classification of hexaferrites, we summarize recent progress in multiferroic hexaferrites, including the mechanisms of spin-induced ferroelectricity, the magnetoelectric phase diagram, giant direct and converse magnetoelectric effects. Furthermore, we present a new mechanism of magnetic-ion-induced displacive polarization in hexaferrites, which leads to quantum paraelectricity and quantum electric-dipole liquid in M-type hexaferrites.

关键词： magnetoelectric effect hexaferrite quantum paraelectricity

sUMs OF DUAL TOEPLITZ PRODUCTs ON THE ORTHOGONAL COMPLEMENTs OF FOCK-sOBOLEV sPACEs

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Acta Mathematica scientia 2024年第3期44卷 810-822页

作者：陈泳 young Joo Lee Department of Mathematics Hangzhou Normal UniversityHangzhou311121China Department of Mathematics Chonnam National UniversityGwangju61186Korea

We consider dual Toeplitz operators on the orthogonal complements of the Focksobolev spaces of all nonnegative real ***,for symbols in a certain class containing all bounded functions,we study the problem of when an operator which is finite sums of the dual Toeplitz products is compact or ***,for bounded symbols,we construct a symbol map and exhibit a short exact sequence associated with the C^(*)-algebra generated by all dual Toeplitz operators with bounded symbols.

关键词： dual Toeplitz operators Fock-sobolev spaces symbol map

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

Therapeutic nucleic acids in regenerative medicine and tissue repair

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Nano Research 2024年第10期17卷 8942-8976页

作者： Qimanguli saiding Duotian Qin soohwan An Dylan neal Patel Muhammad Muzamil Khan Na Kong Wei Tao Center for Nanomedicine and Department of Anesthesiology Brigham and Women’s HospitalHarvard Medical SchoolBostonMassachusetts 02115USA

In the vanguard of biomedical innovation,regenerative medicine emerges as a transformative paradigm,concentrating its efforts on rectifying tissue deficits and functional aberrations in patients through the strategic augmentation of endogenous cellular *** to this approach is nucleic acid therapy,which offers a novel pathway for tissue regeneration by modulating key signaling *** one of the most effective ways to regulate cell function,nucleic acids are crucial for various tissue regeneration;however,their in vivo therapeutic applications face substantial challenges,including nuclease degradation,cell membrane impermeability,and targeted intracellular ***-based gene delivery systems offer a solution for stable and localized drug delivery by enabling the controlled overexpression of therapeutic nucleic acids,producing functional regulatory *** review presents examples of nucleic acid applications in regenerative medicine,highlighting the synergy between nucleic acids and biomaterial *** underlines the importance of nucleic acid delivery techniques,the choice of therapeutic nucleic acids,and biomaterials for advancing tissue *** latest developments in designing nucleic acid biomaterial-based delivery vehicles are explored,the mechanism of nucleic acids in tissue regeneration is elucidated,and their limitations are discussed while considering future directions for the clinical translation of nucleic acid-based therapeutics.

关键词： tissue repair nucleic acids biomaterials delivery systems regenerative medicine

Fabrication of periodically aligned vertical singlecrystalline anatase TiO2 nanotubes with perfect hexagonal open-ends using chemical capping materials

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Nano Research 2014年第1期7卷 104-109页

作者： Hui song Kyubong Jo Bock young Jung Gun young Jung school of Materials science and Engineering Gwangju Institute of Science and Technology (GIST) Gwangju Republic of Korea Department of Chemistry and Interdisciplinary Program of Integrated Biotechnology Sogang University Seoul Republic of Korea Department of General Dentistry College of Dentistry Yonsei University Seoul Republic of Korea

A vertically aligned anatase TiO2 （A-TiO2） nanotube array has been fabricated by coating a ZnO nanorod （NR） template with a TiO2 precursor solution. After coating, the ZnO NR cores were selectively etched in an acidic environment to form TiO2 nanotubes （NTs）. More specifically, after growing the ZnO NRs via a hydrothermal method, one drop of the TiO2 precursor solution was cast to coat the ZnO NRs, the tops of which were previously covered with chemical capping materials by electrostatic interaction, and then the sample was sintered. Finally, the sample was immersed in an acidic solution resulting in selective etching of the ZnO NR cores. Thus, only TiO2 NTs remained on the substrate. The capping material is effectively used to create a perfect, hexagonal open-ended TiO2 NT array, which interestingly extends onset absorption towards the visible region.

关键词： TiO2 nanotubes chemical capping material ZnO nanorod template laser interferencelithography

semi-crystalline photovoltaic polymers with siloxane-terminated hybrid side-chains

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science China Chemistry 2017年第4期60卷 528-536页

作者： Yuxiang Li seyeong song song Yi Park Jin young Kim Han young WOO Department of Cogno-Mechatronics Engineering Pusan National University Miryang 627-706 Republic of Korea Department of Energy and Chemical Engineering Ulsan National Institute of Science and Technology Ulsan 689-798 Republic of Korea Department of Chemistry Korea University Seoul 136-713 Republic of Korea

Three types of semi-cry stalline photovoltaic polymers were synthesized by incorporating a siloxane-terminated organic/inorganic hybrid side-chain and changing the number of fluorine substituents.A branch point away from a polymer main backbone in the siloxane-containing side-chains and the intra-and/or interchain noncovalent coulombic interactions enhance a chain planarity and facile interchain *** resulting polymers formed strongly agglomerated films with high roughness,suggesting strong intermolecular *** optical band gap of ca.1.7 eV was measured for all polymers with a pronounced shoulder peak due to tight π-π *** increasing the fluorine substituents,the frontier energy levels decreased and preferential face-on orientation was *** siloxane-terminated side-chains and fluorine substitution promoted the intermolecular packing,showing well resolved lamellar scatterings up to(300) for this series of polymers in the grazing incidence wide angle X-ray scattering *** PPsiDTBT,PPsiDTFBT and PPsiDT2 FBT devices showed a power conversion efficiency of 3.16%,4.40%and 5.65%,respectively,by blending with PC_(71)***-type bimolecular charge recombination was similar for three polymeric solar *** main loss in the photocurrent generation for PPsiDTBT:PC_(71)BM was interpreted to originate from the trap assisted charge recombination by measuring light-intensity dependent short-circuit current density(J_(sC)) and open-circuit voltage(V_(Oc)).Our results provide a new insight into the rational selection of solubilizing substituents for optimizing crystalline interchain packing with appropriate miscibility with PC71 BM for further optimizing polymer solar cells.

关键词： siloxane side-chain fluorine substitution semi-crystalline charge transport

LINEAR WAVEs THAT EXPREss THE sIMPLEsT POssIBLE PERIODIC sTRUCTURE OF THE COMPREssIBLE EULER EQUATIONs

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Acta Mathematica scientia 2009年第6期29卷 1749-1766页

作者： Blake Temple Robin young Department of Mathematics University of California Davis CA 95616 USA Department of Mathematics and statistics University of Massachusetts Amherst MA 01003 USA

In this paper we show how the simplest wave structure that balances compression and rarefaction in the nonlinear compressible Euler equations can be represented in a solution of the linearized compressible Euler equations. such waves are exact solutions of the equations obtained by linearizing the compressible Euler equations about the periodic extension of two constant states separated by entropy jumps. Conditions on the states and the periods are derived which allow for the existence of solutions in the Fourier 1-mode. In [3, 4, 5] it is shown that these are the simplest linearized waves such that, for almost every period, they are isolated in the kernel of the linearized operator that imposes periodicity, and such that they perturb to nearby nonlinear solutions of the compressible Euler equations that balance compression and rarefaction along characteristics in the formal sense described in [3]. Their fundamental nature thus makes them of interest in their own right.

关键词： compressible Euler periodic solutions conservation laws

Precambrian supercontinents,glaciations,atmospheric oxygenation,metazoan evolution and an impact that may have changed the second half of Earth history

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Geoscience Frontiers 2013年第3期4卷 247-261页

作者： Grant M.young Department of Earth sciences Western University1151 Richmond Street NLondonOntarioCanada N6A 5B7

In more than 4 Ga of geological evolution, the Earth has twice gone through extreme climatic perturba- tions, when extensive glaciations occurred, together with alternating warm periods which were accom- panied by atmospheric oxygenation. The younger of these two episodes of climatic oscillation preceded the Cambrian ＂explosion＂ of metazoan life forms, but similar extreme climatic conditions existed between about 2.4 and 2.2 Ga. Over long time periods, changing solar luminosity and mantle temperatures have played important roles in regulating Earth＇s climate but both periods of climatic upheaval are associated with supercontinents. Enhanced weathering on the orogenically and thermally buoyed supercontinents would have stripped CO2 from the atmosphere, initiating a cooling trend that resulted in continental glaciation. Ice cover prevented weathering so that CO2 built up once more, causing collapse of the ice sheets and ushering in a warm climatic episode. This negative feedback loop provides a plausible explanation for multiple glaciations of the Early and Late Proterozoic, and their intimate association with sedimentary rocks formed in warm climates. Between each glacial cycle nutrients were flushed into world oceans, stimulating photosynthetic activity and causing oxygenation of the atmosphere. Accommodation for many ancient glacial deposits was provided by rifting but escape from the climatic cycle was predicated on break- up of the supercontinent, when flooded continental margins had a moderating influence on weathering. The geochemistry of Neoproterozoic cap carbonates carries a strong hydrothermal signal, suggesting that they precipitated from deep sea waters, overturned and spilled onto continental shelves at the termination of glaciations. Paleoproterozoic （Huronian） carbonates of the Espanola Formation were probably formed as a result of ponding and evaporation in a hydrothermally influenced, restricted rift setting. Why did metazoan evolution not take off a

关键词： Proterozoic supercontinents Glaciations Impacts Oxygenation Metazoa