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Strain tunable band structure of a new 2D carbon allotrope C568

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Journal of Semiconductors 2020年第8期41卷 68-74页

作者： Qiang Gao Hasan Sahin Jun Kang Institute of Semiconductors Chinese Academy of SciencesBeijing 100083China Beijing Computational Science Research Center Beijing 100193China Department of Photonics Izmir Institute of TechnologyIzmirTurkey

Recently,C568 has emerged as a new carbon allotrope,which shows semiconducting properties with a band gap around 1 eV and has attracted much *** this work,the external strain effects on the electronic properties of C568 have been studied theoretically through first-principle *** numerical results show that while in-plane uniaxial and biaxial strains both reduces the band gap of C568 in case of tensile strain,their effects are quite different in the case of compressive *** increasing compressive uniaxial strain,the band gap of C568 first increases,and then dramatically *** contrast,the application of compressive biaxial strain up to -10% only leads to a slight increase of band ***,an indirect-todirect gap transition can be realized under both types of compressive *** results also show that the optical anisotropy of C568 can be induced under uniaxial strain,while biaxial strain does not cause such an *** results indicate good strain tunability of the band structure of C568,which could be helpful for the design and optimization of C568-based nanodevices.

关键词： 2D C568 monoelemental 2D atomic crystalline materials strain effects electronic structures

LARGE EDDY SIMULATION OF COMPLEX TURBULENT FLOWS:PHYSICAL ASPECTS AND RESEARCH TRENDS

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Acta Mechanica Sinica 2001年第4期17卷 289-301页

作者：李家春 DES Institute of MechanicsCASBeijing 100080China

In the current paper, we have primarily addressed one powerful simulation tool developed during the last decades-Large Eddy Simulation (LES), which is most suitable for unsteady three-dimensional complex turbulent flows in industry and natural environment. The main point in LES is that the large-scale motion is resolved while the small-scale motion is modeled or, in geophysical terminology, parameterized. With a view to devising a subgrid-scale(SGS) model of high quality, we have highlighted analyzing physical aspects in scale interaction and-energy transfer such as dissipation, backscatter, local and non-local interaction, anisotropy and resolution requirement. They are the factors responsible for where the advantages and disadvantages in existing SGS models come from. A case study on LES of turbulence in vegetative canopy is presented to illustrate that LES model is more based on physical arguments. Then, varieties of challenging complex turbulent flows in both industry and geophysical fields in the near future-are presented. In conclusion; we may say with confidence that new century shall see the flourish in the research of turbulence with the aid of LES combined with other approaches.

关键词： LES energy dissipation backscatter local and non-local interaction SGS model

Performance measurement and evaluation of an ionic liquid electrospray thruster

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Chinese Journal of Aeronautics 2023年第3期36卷 1-15页

作者： Chengjin HUANG Jianling LI Mu LI School of Power and Energy Northwestern Polytechnical UniversityXi’an 710072China Shenzhen Key Laboratory of Ultraintense Laser and Advanced Material Technology Center for Advanced Material Diagnostic Technologyand College of Engineering PhysicsShenzhen Technology UniversityShenzhen 518118China

As a novel micro-propulsion system for small satellites(from micro to nano),the ionic liquid electro spray propulsion system is a promising ***,performance measurement and evaluation of the Ionic Liquid Electrospray Thruster(ILET)is one of the most challenging issues for practical application,due to the difficulties in the development of a prototype and direct measurements of micro-thrust and small flow *** address this issue,a Modular Ionic Liquid Electrospray Thruster(MILET)prototype is constructed,and a diagnostic system for thrust and mass flow rate is specially developed based on an analytical balance *** the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate as the propellant,a series of experiments is carried out on the MILET prototype under a wide operating condition through changing the applied voltage to control the *** different applied voltages,the thrust and the mass flow rate of the propellant are directly *** propulsive performance parameters of the thruster,such as thrust,specific impulse,thrust-to-power ratio,thruster efficiency,etc.,are comprehensively ***,a performance comparison is made between the MILET and other representative *** a relatively low applied voltage ranging from 1550 V to 2000 V,the MILET achieves a quasi-constant specific impulse of 1263 s with the averaged thrust-to-power ratio of 65.2μN/W and thruster efficiency of 40.7%.The performance of ILET is also compared with other typical electric *** results demonstrate that the ILET exhibits an excellent ability of minimalization with high specific impulse and thruster efficiency,which guarantees a great superiority in micro ***,the ways to further improve the performance of ILET are discussed,which further confirms the potential prospect of *** present result helps to advance the development and application of ILET.

关键词： Electrospray thruster Ionic liquids Performance measurement Performance estimation Micro-propulsion

CMOS-compatible retinomorphic Si photodetector for motion detection

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Science China(Information Sciences) 2023年第6期66卷 242-249页

作者： Yi WU Wenjie DENG Xiaoqing CHEN Jingjie LI Songyu LI Yongzhe ZHANG Faculty of Materials and Manufacturing Beijing University of Technology Key Laboratory of Optoelectronics Technology of Education Ministry of China Faculty of Information TechnologyBeijing University of Technology School of Physics Beihang University

Efficient motion detection is essential for the Internet of Things. However, it suffers from overloading redundant static background information. Inspired by the human visual system, which is efficient in motion detection, we propose a silicon-based retinomorphic photodetector with a simple metal/insulator/semiconductor(MIS)structure, which is compatible with the complementary metal-oxide-semiconductor(CMOS)industry. In contrast to conventional photodetectors that generate a sustained photocurrent, our retinomorphic photodetector is sensitive only to the change in light intensity and therefore filters the redundant static background. In addition, it shows logarithmic dependence on the light intensity, which simplifies the contrast ratio measurement. Based on our moving object recognition experiment, after filtering background information, the information to be analyzed is reduced to 27.3%, thereby improving the image recognition efficiency in the subsequent processing tasks. This innovative and industry-compatible retinomorphic photodetector will facilitate the construction of future efficient motion detection systems.

关键词： retina photodetector motion detection bio-inspired in-sensor computing

STRONG SOLUTIONS OF THE COUPLED NAVIER-STOKES-POISSON EQUATIONS FOR ISENTROPIC COMPRESSIBLE FLUIDS

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Acta Mathematica Scientia 2010年第4期30卷 1280-1290页

作者：谭忠张映辉 School of Mathematical Sciences Xiamen University Department of Mathematics Hunan Institute of Science and Technology

In this article, we are concerned with the strong solutions of the coupled Navier-Stokes-Poisson equations for isentropic compressible fluids in a domain Ω R^3. We prove the local existence of unique strong solutions provided that the initial data u0 and u0 satisfy a nature compatibility condition. The important point in this article is that we allow the initial vacuum： the initial density may vanish in an open subset of Ω. This is achieved by getting some uniform estimates and using a Schauder fixed point theorem.

关键词： Strong solutions Navier-Stokes-Poisson equations Schauder fixed point theorem

Light-induced magnetic phase transition in van der Waals antiferromagnets

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Science China(Physics,Mechanics & Astronomy) 2023年第7期66卷 136-141页

作者： Jiabin Chen Yang Li Hongyu Yu Yali Yang Heng Jin Bing Huang Hongjun Xiang Key Laboratory of Computational Physical Sciences(Ministry of Education) Institute of Computational Physical SciencesState Key Laboratory of Surface PhysicsDepartment of PhysicsFudan UniversityShanghai 200433China Shanghai Qi Zhi Institute Shanghai 200030China Beijing Computational Science Research Center Beijing 100193China Department of Physics Beijing Normal UniversityBeijing 100193China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093China

Control over magnetic properties by optical stimulation is not only interesting from the physics point of view,but also important for practical applications such as magneto-optical ***,based on a simple tight-binding(TB)model,we propose a general theory of light-induced magnetic phase transition(MPT)in *** the fact that the bandgap of the antiferromagnetic(AFM)phase is usually larger than that of the ferromagnetic(FM)one for a given system,we suggest that light-induced electronic excitation prefers to stabilize the FM state over the AFM one,and will induce an MPT from AFM phase to FM phase once a critical photocarrier concentration(αc)is *** theory has been confirmed by performing firstprinciples calculations on a series of 2D van der Waals(vd W)***,a linear relationship betweenαc and the intrinsic material parameters is obtained,in agreement with our TB model *** general theory paves a new way to manipulate 2D magnetism with high speed and superior resolution.

关键词： first-principles calculation density functional theory two-dimensional materials magnetic phase transition

Tuning the reactivity of Al-Ni by fine coating of halogen-containing energetic composites

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Defence Technology（防务技术） 2022年第10期18卷 1810-1821页

作者： Su-lan Yang Ke-juan Meng Wu-xi Xie Hong-qi Nie Qi-Long Yan Science and Technology on Combustion Internal Flow and Thermo-Structure LaboratoryNorthwestern Polytechnical UniversityXi'an710072China b Xi'an Modern Chemistry Research Institute Xi'an710065China

In this paper,various core-shell structured Al—Ni@ECs composites have been prepared by a spray-drying *** involved ECs refer to the energetic composites(ECs)of ammonium perchlorate/nitrocellulose(AP/NC,NA)and polyvinylidene fluoride/hexanitrohexaazaisowurtzitane(PVDF/CL-20,PC).Two Al—Ni mixtures were prepared at atomic ratios of 1:1 and 1:3 and named as Al/Ni and Al/3Ni,*** thermal reactivity and combustion behaviors of Al—Ni@ECs composites have been comprehensively *** showed that the reactivity and combustion performance of Al—Ni could be enhanced by introducing both NA and PC energetic *** which the Al/Ni@NA composite exhibited higher reactivity and improved combustion *** measured flame propagation rate(v=20.6 mm/s),average combustion wave temperature(T_(max)=1567.0°C)and maximum temperature rise rate(γ_(t)=1633.6°C/s)of Al/Ni@NA are higher than that of the Al/Ni(v=15.8 mm/s,T_(max)=858.0°C,andγ_(t)=143.5°C/s).The enhancement in combustion properties could be due to presence of the acidic gaseous products from ECs,which could etch the Al_(2)O_(3)shell on the surface of Al particles,and make the inner active Al to be easier transported,so that an intimate and faster intermetallic reaction between Al and Ni would be ***,the morphologies and chemical compositions of the condensed combustion products(CCPs)of Al—Ni@ECs composites were found to be different depending on the types of *** compositions of CCPs are dominated with the Al—Ni intermetallics,combining with a trace amount of Al_(5)O_(6)N and Al_(2)O_(3).

关键词： Arrested high energy ball milling Intermetallic alloy Combustion performance Energetic composites Reactivity control

Simple point contact WO_3 sensor for NO_2 sensing and relevant impedance analysis

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International Journal of Minerals,Metallurgy and Materials 2012年第12期19卷 1142-1148页

作者： Wu-bin Gao Yun-han Ling Xu Liu Jia-lin Sun School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Department of Materials Science and Engineering Tsinghua University Beijing 100084 China

A simple and new point contact tungsten trioxide （WO3） sensor, which can be prepared by the oxidation of tungsten filaments via in-situ induction heating, likely detects low concentration （ppm level） environmental pollutants such as NO2. X-ray diffraction （XRD） and field emission scanning electron microscopy （FE-SEM） were applied to characterize the phase and the microstructure of the samples, respec-tively. It was found that the synthesized WO3 films exhibited a monoclinic phase and were composed of hierarchical microcrystals and nanocrystals. The point contact WO3 sensor （W-WO3-W） showed rectifying characteristics and an ideal sensing performance of about 110 C. A single semicircle in Nyquist plots was recorded by electrochemical impedance spectroscopy （EIS） at a relatively low temperature of 150 C but faded away above 200 C, which revealed that the sensing process was governed by a determining factor, i.e., grain boundaries at the contact site.

关键词： gas sensors tungsten trioxide metal oxide semiconductors thin fills microcrystals nanocrystals electrochemical impedancespectroscopy (EIS)

CLASSIFICATION OF SOLUTIONS FOR A CLASS OF SINGULAR INTEGRAL SYSTEM

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Acta Mathematica Scientia 2011年第4期31卷 1449-1456页

作者：许建开谭忠 College of Sciences Hunan Agriculture University School of Mathematical Sciences Xiamen University

In this paper, we consider the following integral system： u（x） = R n v q （y）｜ x y ｜ nα dy, v（x） = R n u p （y）｜ x y ｜ nμ dy, （0.1） where 0 〈 α, μ 〈 n; p, q ≥ 1. Using the method of moving planes... 详细信息

In this paper, we consider the following integral system： u（x） = R n v q （y）｜ x y ｜ nα dy, v（x） = R n u p （y）｜ x y ｜ nμ dy, （0.1） where 0 〈 α, μ 〈 n; p, q ≥ 1. Using the method of moving planes in an integral form which was recently introduced by Chen, Li, and Ou in [2, 4, 8], we show that all positive solutions of （0.1） are radially symmetric and decreasing with respect to some point under some general conditions of integrability. The results essentially improve and extend previously known results [4, 8].

关键词： Hardy-Littlewood-Sobolev inquality integral equation moving plane interpolation inequality radial symmetry