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theoretical prediction,synthesis,and crystal structure determination of new MAX phase compound V2.nC

Journal of Advanced Ceramics 2020年第4期9卷 481-492页

作者： Qiang Xu Yanchun zhou haiming Zhang Anna Jiang Quanzheng Tao {2. Lu Johanna Rosén Yunhui Niu Salvatore Grasso Chunfeng Hu Key Laboratory of Advanced Technologies of Materials Ministry of EducationSchool of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu610031China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing100076China School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing100044China Thin Film physics Division Department of PhysicsChemistryand Biology(IFM)Linköping UniversityLinköpingSE-58183Sweden State Key Laboratory of Environment-friendly Energy Materials Southwest University of Science and TechnologyMianyang621010China

Guided by the theoretical prediction,a new MAX phase V2.nC was synthesized experimentally for the first time by reaction of V,Sn,and C mixtures at 1000°*** chemical composition and crystal structure of this new compound were identified by the cross-check combination of first-principles calculations,X-ray diffraction(XRD),energy dispersive X-ray spectroscopy(EDS),and high resolution scanning transmission electron microscopy(HR-STEM).The stacking sequence of V2. and Sn layers results in a crystal structure of space group P63/*** a-and c-lattice parameters,which were determined by the Rietveld analysis of powder XRD pattern,are 0.2.81(0)nm and 1.3470(6)nm,*** atomic positions are V at 4f(1/3,2.3,0.0776(5)),Sn at 2.(2.3,1/3,1/4),and C at 2.(0,0,0).A new set of XRD data of V2.nC was also *** calculations suggest that this new compound is stable with negative formation energy and formation enthalpy,satisfied Born-Huang criteria of mechanical stability,and positive phonon branches over the Brillouin *** also has low shear deformation resistance c44(second-order elastic constant,cij)and shear modulus(G),positive Cauchy pressure,and low Pugh’s ratio(G/B=0.500<0.571),which is regarded as a quasi-ductile MAX *** mechanism underpinning the quasi-ductility is associated with the presence of a metallic bond.

关键词： V2.nC new MAX phase compound crystal structure first-principles calculations

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Old stellar population synthesis:new age and mass estimates for Mayall II = G1

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Research in Astronomy and Astrophysics 2009年第6期9卷 641-652页

作者： jun Ma Richard de Grijs zhou Fan Soo-Chang Rey Zhen-Yu Wu Xu zhou Jiang-Hua Wu Zhao-Ji Jiang Jian-Sheng Chen Kyungsook Lee Sangmo Tony Sohn National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Department of physics ＆ Astronomy The University of Sheffield Hicks Building Hounsfield Road Sheffield S3 7RH UK Graduate University Chinese Academy of Sciences Beijing 100049 China Department of Astronomy and Space Science Chungnam National University Daejeon 305-764 Korea Center for Space Astrophysics Yonsei University Seoul 120-749 Korea California institute of Technology MC 405-47 1200 E. California Boulevard Pasadena CA 91125

Mayall Ⅱ = G1 is one of the most luminous globular clusters （GCs） in M31. Here, we determine its age and mass by comparing multicolor photometry with theoretical stellar population synthesis models. Based on far- and near-ultraviolet GALEX photometry, broad-band UBVRI, and infrared JHKs 2.ASS data, we construct the most extensive spectral energy distribution of G 1 to date, spanning the wavelength range from 1538 to 2. 000A. A quantitative comparison with a variety of simple stellar population （SSP） models yields a mean age which is consistent with G1 being among the oldest building blocks of M31 and having formed within ～1.7 Gyr after the Big Bang. Irrespective of the SSP model or stellar initial mass function adopted, the resulting mass estimates （of order 10^7M⊙） indicate that GI is one of the most massive GCs in the Local Group. However, we speculate that the cluster＇s exceptionally high mass suggests that it may not be a genuine GC. Our results also suggest that G1 may contain, on average, （1.65±0.63） × 10^2.⊙ far-ultraviolet-bright, hot, extreme horizontal-branch stars, depending on the adopted SSP model. In addition, we demonstrate that extensive multi-passband photometry coupled with SSP analysis enables one to obtain age estimates for old SSPs that have similar accuracies as those from integrated spectroscopy or resolved stellar photometry, provided that some of the free parameters can be constrained independently.

关键词： galaxies individual (M31) -- galaxies star clusters -- galaxies stellar content

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The role of aromatic residues in controlling the supramolecular chirality of short amphiphilic peptides

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Nano Research 2023年第10期16卷 12230-12237页

作者： Hao Qi Kai Qi Jie Li Chunyong He Mingrui Liao Xuzhi Hu Yurong Zhao Yubin Ke Chunqiu Zhang jun Zhang Jiqian Wang Jian R.Lu hai Xu Department of Biological and Energy Chemical Engineering China University of Petroleum(East China)Qingdao 266580China College of Life Science Nankai UniversityTianjin 300071China Spallation Neutron Source Science Center Chinese Academy of Sciences(CAS)Dongguan 523803China institute of High Energy physics Chinese Academy of SciencesBeijing 100049China Biological physics Group Department of Physics and AstronomyThe University of ManchesterManchester M139PLUK School of Material Science and Engineering China University of Petroleum(East China)Qingdao 266580China

Although the relationship between molecular and supramolecular chirality remains elusive,the existing results have demonstrated the vital role of hydrophilic motifs in controlling the supramolecular handedness of peptide nanofibrils compared with hydrophobic ***,unlike conventional hydrophobic residues,we speculate that aromatic hydrophobic residues are mostly likely to play a unique role in regulating the supramolecular handedness because theπ–πstacking interactions of their side chains are directional like hydrogen bonding and can direct high levels of self-assembly due to the geometric confining of aromatic *** confirm this hypothesis,we here design a series of amphiphilic short peptides,with their hydrophobic motifs being composed of aromatic *** short lengths not only favor their structural stability,synthesis,and sequence variation but also enable us to readily link their molecular and supramolecular *** the combination of experiments and theoretical simulations,we demonstrate that the peptides containing L-form aromatic residues form left-handed nanofibrils while those containing D-form aromatic residues assemble into right-handed ones,irrespective of the chirality of their C-terminal hydrophilic *** calculations revealed that the stacking of aromatic side chains betweenβ-strands directed the twisting direction of theβ-sheets formed,with L-and D-form phenylalanine side chains stacking in a clockwise and anti-clockwise way,and more ordered and stronger aromatic stacking for homochiral peptides facilitated the formation of nanofibrils with a marked tubular *** study has bridged the knowledge gap in our understanding of how aromatic residues affect the supramolecular chirality of short peptides.

关键词： amphiphilic short peptide molecular chirality supramolecular handedness aromatic residue π–πstacking

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Competition Between Pairing and Anti-pairing Correlations in the Superdeformed Nuclear States in A~l90 and 150 Ranges

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Chinese physics Letters 1997年第9期14卷 641-644页

作者： LIU Yu-xin SONG Jian-gang SUN Hong-zhou WANG Jia-jun ZHAO En-guang Department of physics Peking Universitx Beijing 100871 Department of physics Tsinghua UniversityBeijing 100084 institute of theoretical {2. Chinese Academy of SciencesBeijing 100080

An approach considering both pairing and anti-pairing correlations in superdeformed(SD)states is *** results show that not only the general changing feature but also the turnover of dynamical moment of inertia with rotational frequency of the first SD band of ^(192.Hg,^(194)Hg,and ^(152.Dy are well described in the *** indicates that there exist competition,even change-over between the anti-pairing and pairing effects in the SD states in A~190 and 150 ranges.

关键词： inertia states pairing

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Reconstruction and interpretation of photon Doppler velocimetry spectrum for ejecta particles from shock-loaded sample in vacuum

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Chinese physics B 2021年第6期30卷 419-429页

作者： Xiao-Feng Shi Dong-jun Ma Song-lin Dang Zong-Qiang Ma hai-Quan Sun An-Min He Pei Wang institute of Applied Physical and Computational Mathematics Beijing 100094China Jiangxi University of Applied Science Nanchang 330103China Center for Applied physics and Technology Peking UniversityBeijing 100871China

The photon Doppler velocimetry(PDV) spectrum is investigated in an attempt to reveal the particle parameters of ejecta from shock-loaded samples in a vacuum. A GPU-accelerated Monte–Carlo algorithm, which considers the multiplescattering effects of light, is applied to reconstruct the light field of the ejecta and simulate the corresponding PDV *** influence of the velocity profile, total area mass, and particle size of the ejecta on the simulated spectra is discussed qualitatively. To facilitate a quantitative discussion, a novel theoretical optical model is proposed in which the singlescattering assumption is applied. With this model, the relationships between the particle parameters of ejecta and the peak information of the PDV spectrum are derived, enabling direct extraction of the particle parameters from the PDV *** values of the ejecta parameters estimated from the experimental spectrum are in good agreement with those measured by a piezoelectric probe.

关键词： ejecta photon Doppler velocimetry Monte–Carlo algorithm light scattering

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Slow Light Effect and Multimode Lasing in a Photonic Crystal Waveguide Microlaser

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Chinese physics Letters 2010年第2期27卷 123-126页

作者：邢名欣郑婉华周文君陈微刘安金王海玲 Nano-optoelectronics Lab Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 State Key Laboratory on Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Sciences Beijing 100083

The slow light effect in a photonic crystal waveguide is investigated theoretically and experimentally. theoretical calculation indicates that there is a slow light region for the even mode, from which the resonance and lasing in a microcavity would benefit. A photonic crystal waveguide microlaser is fabricated, which is related to the group velocity of c/12..6.

关键词： Chinese climate network complex systems small world community

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An efficient route to prepare suspended monolayer for feasible optical and electronic characterizations of two-dimensional materials

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InfoMat 2022年第2期4卷 126-138页

作者： Yuan Huang Yun-Kun Wang Xin-Yu Huang Guan-Hua Zhang Xu Han Yang Yang Yunan Gao Lei Meng Yushu Wang Guang-zhou Geng Li-Wei Liu Lin Zhao Zhi-hai Cheng Xin-Feng Liu Ze-Feng Ren Hui-Xia Yang Yufeng Hao Hong-{2. Gao Xing-Jiang zhou Wei Ji Ye-Liang Wang Advanced Research institute of Multidisciplinary Science Beijing Institute of TechnologyBeijingChina beijing National Laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of SciencesBeijingChina Songshan Lake Materials Laboratory DongguanChina State Key Laboratory for Artificial Microstructure and Mesoscopic physics School of PhysicsPeking UniversityBeijingChina Frontiers Science Center for Nanooptoelectronics&Collaborative Innovation Center of Quantum Matter BeijingChina State Key Laboratory of Molecular Reaction Dynamics Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalianChina Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuanChina Minzu University of china BeijingChina National Laboratory of Solid State Microstructures College of Engineering and Applied SciencesJiangsu Key Laboratory of Artificial Functional MaterialsCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjingChina School of Information and Electronics MIIT Key Laboratory for Low-Dimensional Quantum Structure and DevicesBeijing Institute of TechnologyBeijingChina Department of physics and beijing Key Laboratory of Optoelectronic Functional Materials&Micro-Nano Devices Renmin University of ChinaBeijingChina National Center for Nanoscience and Technology(NCNST)of china BeijingChina haian institute of New Technology Nanjing UniversityHaianChina University of Chinese academy of sciences BeijingChina

Two-dimensional(2.)materials are highly sensitive to substrates,interfaces,and the surrounding *** 2. materials are free from substrate-induced effects,thus an ideal approach to study their intrinsic ***,it is very challenging to prepare large-area suspended 2. materials with high *** we report a universal method,based on pretreatments of densely patterned hole array substrates with either oxygenplasma or gold film deposition,to prepare large-area suspended mono-and few-layer 2. *** structural,optical,and electrical characterization tools were used to fully evaluate the improved performance of various suspended 2. *** of these observations reported in this study are:(1)Observation of a new Raman low frequency mode for the suspended MoS_(2.;(2.Significantly stronger photoluminescence(PL)and second harmonic generation(SHG)signals of suspended WSe_(2.,which enables the study of new optical transition processes;(3)The low energy electron diffraction pattern on suspended MoS_(2. also exhibits much sharper spots than that on the supported area;and(4)The mobility of suspended graphene device approaches 300000 cm^(2. V^(-1) s^(-1),which is desirable to explore the intrinsic properties of *** work provides an innovative and efficient route for fabricating suspended 2. materials,and we expect that it can be broadly used for studying intrinsic properties of 2. materials and in applications of hybrid active nanophotonic and electronic devices.

关键词： mechanical exfoliation photoluminescence Raman spectrum suspended 2. materials

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Wet etching and passivation of GaSb-based very long wavelength infrared detectors

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Chinese physics B 2022年第6期31卷 132-136页

作者： Xue-Yue Xu jun-Kai Jiang Wei-Qiang Chen Su-Ning Cui Wen-Guang zhou Nong Li Fa-Ran Chang Guo-Wei Wang Ying-Qiang Xu Dong-Wei Jiang Dong-{2. Wu Hong-Yue Hao Zhi-Chuan Niu State Key Laboratory for Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China College of Materials Science and Opto-Electronic Technology University of Chinese Academy of SciencesBeijing 100049China

The etching and passivation processes of very long wavelength infrared(VLWIR)detector based on the InAs/GaSb/AlSb type-II superlattice have been *** studying the effect of each component in the citric acid solution(citric acid,phosphoric acid,hydrogen peroxide,deionized water),the best solution ratio is *** comparing different passivation materials such as sulfide+SiO_(2.,Al_(2.O_(3),Si_(3)N_(4) and SU8,it is found that SU8 passivation can reduce the dark current of the device to a greater *** this wet etching and SU8 passivation,the of VLWIR detector with a mesa diameter of 500μm is about 3.6Ω·cm^(2. at 77 K.

关键词： InAs/GaSb/AlSb superlattice very long wavelength infrared(VLWIR)detector wet etching passivation

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Containment consensus with measurement noises and time-varying communication delays

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Chinese physics B 2015年第2期24卷 23-29页

作者：周峰王正杰范宁军 School of Electromechanical Engineering Beijing Institute of Technology

In this paper,we consider the containment consensus control problem for multi-agent systems with measurement noises and time-varying communication delays under directed *** using stochastic analysis tools and algebraic graph theory,we prove that the followers can converge to the convex hull spanned by the leaders in the sense of mean square if the allowed upper bound of the time-varying delays satisfies a certain sufficient ***,the time-varying delays are asymmetric for each follower agent,and the time-delay-dependent consensus condition is ***,numerical simulations are provided to illustrate the effectiveness of the obtained theoretical results.

关键词： multi-agent systems containment consensus noise communication delays

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Optimization of terahertz monolithic integrated frequency multiplier based on trap-assisted physics model of THz Schottky barrier varactor

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Chinese physics B 2020年第10期29卷 308-314页

作者： Lu-Wei Qi Jin Meng Xiao-Yu Liu Yi Weng Zhi-Cheng Liu De-hai Zhang Jing-Tao zhou Zhi Jin institute of Microelectronics of the Chinese academy of {2. Beijing 100029China National Space Science Center the Chinese Academy of SciencesBeijing 100190China University of Chinese academy of sciences Beijing 100190China

The optimization of high power terahertz monolithic integrated circuit (TMIC) is systemically studied based on the physical model of the Schottky barrier varactor (SBV) with interface defects and tunneling effect. An ultra-thin dielectric layer is added to describe the extra tunneling effect and the damping of thermionic emission current induced by the interface defects. Power consumption of the dielectric layer results in the decrease of capacitance modulation ration (Cmax/Cmin), and thus leads to poor nonlinear C–V characteristics. The proposed Schottky metal-brim (SMB) terminal structure could improve the capacitance modulation ration by reducing the influence of the interface charge and eliminating the fringing capacitance effect. Finally, a 2.5 GHz tripler TMIC is fabricated based on the SMB terminal structure. The output power is above 5 mW at 2.0–2.8 GHz and the maximum could exceed 10 mW at 2.6 GHz, which could be widely used in terahertz imaging, radiometers, and so on. This paper also provides theoretical support for the SMB structure to optimize the TMIC performance.

关键词： C-V characteristic physics-based model terahertz monolithic integrated circuit(TMIC) Schottky barrier varactor

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