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Chinese Journal of Aeronautics 2017年第6期30卷 1985-2003页

作者： Yujie si Shenmin song Center for Control Theory and Guidance Technology Harbin Institute of Technology Harbin 150001 China

To intercept maneuvering targets at desired impact angles, a three-dimensional terminal guidance problem is investigated in this study. Because of a short terminal guidance time, a finitetime impact angle control guidance law is developed using the fast nonsingular terminal sliding mode control theory. However, the guidance law requires the upper bound of lumped uncertainty including target acceleration, which may not be accurately obtained. Therefore, by adopting a novel reaching law, an adaptive sliding mode guidance law is provided to release the drawback. At the same time, this method can accelerate the convergence rate and weaken the chattering phenomenon to a certain extent. In addition, another novel adaptive guidance law is also derived; this ensures systems asymptotic and finite-time stability without the knowledge of perturbations *** simulations have demonstrated that all the three guidance laws have effective performances and outperform the traditional terminal guidance laws.

关键词： Adaptive control Finite-time guidance law Impact angle Sliding mode control Three-dimensional guidance law

Numerical investigation of separation-induced transition in a lowpressure turbine cascade in a low-disturbance environment

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Science China(Physics,Mechanics & Astronomy) 2020年第6期63卷 66-82页

作者： si-Ya jiang song Fu School of Aerospace Engineering Tsinghua UniversityBeijing 100084China

In this paper,the separation-induced transition in an LPT(low-pressure turbine)cascade is investigated at low Reynolds number with DNS(direct numerical simulation).The transition process is accurately predicted giving good agreements between the DNS and experimental *** illustrate the secondary instability of separation-induced transition in a low-disturbance environment,the results are comprehensively analyzed in both Fourier space and physical *** is illustrated that the effect of hyperbolic instability dominates around the saddle point of hyperbolic *** instability mechanism is responsible for the emergence of the streamwise vortices in the braid *** and intensified because of the“stretching”effect of the background flow,these vortices become the most noticeable characteristic of the flow *** modes of small spanwise wavelength are excited in the braid region,so as some low-frequency *** elliptical instability plays a minor role than hyperbolic *** is also observed that the fundamental mode with a larger spanwise wavelength is unstable in the vortex core which is associated with the deformation of the vortex core via elliptical *** is no convincing evidence for the existence of subharmonic instability.

关键词： separation direct numerical simulation transition to turbulence

Dual-modification of manganese oxide by heterostructure and cation pre-intercalation for high-rate and stable zinc-ion storage

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Journal of Energy Chemistry 2022年第4期31卷 82-91页

作者： song Wang Weibing Ma Zhiyuan Sang Feng Hou Wenping si jingdong Guo ji Liang De'an Yang Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education School of Materials Science and EngineeringTianjin UniversityTianjin 300072China

Zinc-ion batteries(ZIBs)possess great advantages in terms of high safety and low cost,and are regarded as promising alternatives to lithium-ion batteries(LIBs).However,limited by the electrochemical kinetics and structural stability of the typical cathode materials,it is still difficult to simultaneously achieve high rates and high cycling stability for ***,we present a manganese oxide(Sn_(x)Mn O_(2)/Sn O_(2))material that is dual-modified by Sn O_(2)/Mn O_(2)heterostructures and pre-intercalated Sn;cations as the cathode material for *** modification provides sufficient hetero-interfaces and expanded interlayer spacing in the material,which greatly facilitates the insertion/extraction of Zn^(2+).Meanwhile,the“structural pillars”of Sn^(4+) cations and the“pinning effect”of SnO_(2)also structurally stabilizes the Mn O_(2)species during the repeated Zn^(2+) insertion/extraction,leading to ultra-high cycling *** to these merits,the Sn_(x)MnO_(2)/SnO_(2)cathode exhibits a high reversible capacity of 316.1 m Ah g^(-1) at 0.3 A g^(-1),superior rate capability of 179.4 m Ah g^(-1) at 2 A g^(-1),and 92.4%capacity retention after 2000 ***,this work would provide a promising yet efficient strategy by combining heterostructures and cations preintercalation to obtain high-performance cathodes for ZIBs.

关键词： Zinc-ion battery Manganese-based cathode material Pre-intercalation Heterostructure

Fermi Blazars in the Zwicky Transient Facility Survey:Properties of Large Optical Variations

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Research in Astronomy and Astrophysics 2024年第10期24卷 104-115页

作者： si-si Sun Zhong-Xiang Wang Shun-Hao ji Department of Astronomy School of Physics and AstronomyYunnan UniversityKunming 650091China Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China

We analyze the optical light curve data,obtained with the Zwicky Transient Facility(ZTF)survey,for 47 γ-ray blazars monitored by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope(Fermi).These 47sources are selected because they are among the Fermi blazars with the largest optical variations in the ZTF *** color-magnitude variation patterns are seen in them,with one being redder-to-stable-when-brighter(RSWB;in 31 sources)and the other being stable when brighter(in 16 sources).The patterns fit with the results recently reported in several similar studies with different ***,we find that the colors in the stable state of the sources share similar values,for which(after being corrected for the Galactic extinction)most sources are in a range of 0.4–*** feature could be intrinsic and may be applied in,for example,study of the intragalactic *** also determine the turning points for the sources showing the RSWB pattern,after which the color changes saturate and become *** find a correlation between optical fluxes and γ-ray fluxes at the turning *** physical implications of the correlation remain to be investigated,probably better with a sample of high-qualityγ-ray flux measurements.

关键词： (galaxies:)BL Lacertae objects:general (galaxies:)quasars:general gamma-rays:galaxies

The Attractor of Fibonacci-like Renormalization Operator

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Acta Mathematica sinica,English Series 2020年第11期36卷 1256-1278页

作者： Hao Yang ji si Min LI School of Matherratical Sciences Uriversitgy of Science anad Technology of ChinaHefei 230026P.R.Chinra

In this paper we extend the Fibonacci-like maps to a wider class with the so-called“bounded combinatorics”.The Fibonacci-like renormalization operator R is defined and we showthat the orbit of each map from this cla... 详细信息

关键词： Fibonacci combinatorics principal nest renormalization

Time-Inconsistent Stochastic LQ Problem with Regime Switching

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Journal of Systems Science & Complexity 2020年第6期33卷 1733-1754页

作者： si Binbin NI Yuan-Hua ZHANG ji-Feng College of Artificial Intelligence Nankai UniversityTianjin 300350China Key Laboratory of IntelligentRobotics of Tianjin Tianjin 300350China Key Laboratory of Systems and Control Academy of Mathematics and Systems ScienceChinese Academy ofSciencesBeijing 100190China School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100049China

This paper investigates a time-inconsistent stochastic linear-quadratic problem with regime switching that is characterized via a finite-state Markov ***-loop equilibrium control is studied in this paper whose existence is characterized via Markov-chain-modulated forward-backward stochastic difference equations and generalized Riccati-like equations with jumps.

关键词： Forward-backward stochastic difference equation open-loop equilibrium control regime switching stochastic linear-quadratic problem time inconsistency

Exciton radiative lifetime in CdSe quantum dots

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Journal of Semiconductors 2023年第3期44卷 104-113页

作者： Zhimin ji Zhigang song State Key Laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

Colloidal CdSe quantum dots(QDs)are promising materials for solar cells because of their simple preparation pro-cess and compatibility with flexible *** QD radiative recombination lifetime has attracted enormous attention as it affects the probability of photogenerated charges leaving the QDs and being collected at the battery ***,the scaling law for the exciton radiative lifetime in CdSe QDs is still a *** article presents a novel explanation that recon-ciles this *** calculations agree with the experimental measurements of all three divergent trends in a broadened energy ***,we proved that the exciton radiative lifetime is a consequence of the thermal average of decays for all thermally accessible exciton *** of the contradictory size-dependent patterns reflects this trend in a specific size *** the optical band gap increases,the radiative lifetime decreases in larger QDs,increases in smaller QDs,and is weakly depend-ent on size in the intermediate energy *** study addresses the inconsistencies in the scaling law of the exciton life-time and gives a unified interpretation over a widened ***,it provides valuable guidance for carrier separa-tion in the thin film solar cell of CdSe QDs.

关键词： solar cells CdSe quantum dot radiative lifetime scaling law optical band gap exciton fine structure room temperat-ure

Thermal fatigue behavior of K125L superalloy

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Rare Metals 2016年第2期35卷 172-176页

作者： Li-Kui Ning Zhi Zheng Feng-Quan An song Tang jian Tong Hui-si ji Hui-Wen Yu Institute of Metal Research Chinese Academy of Sciences Material Preparation Company Northern Heavy Industries Group Co. Ltd.

The thermal fatigue behavior of K125 L superalloy at the peak temperature of 1,050 °C was investigated by optical microscope（OM）, X-ray diffraction（XRD）, and scanning electron microscope（SEM）. The experimental results show that the crack initiation sites of tested alloys are at the V-notch tip and the V-notch tip propagates by way of continuous cracking along grain boundaries. The formation of high-temperature oxides and MC carbides accelerates the crack propagation, and no secondary carbides precipitate out. Oxides between cracks are mainly the Al2O3 as well as Cr_2O_3, and carbides are Ta-rich and Tirich MC carbides.

关键词： K125L superalloy Thermal fatigue High temperature oxidation Carbides

Asymptotic Estimates to Non-global Solutions of a Multi-coupled Parabolic System

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Acta Mathematica sinica,English Series 2008年第10期24卷 1713-1726页

作者： Rui Hong ji si Ning ZHENG Department of Applied Mathematics Dalian University of Technology Dalian 116024 P. R. China

This paper deals with asymptotic behavior of solutions to a parabolic system, where two heat equations with inner absorptions are multi-coupled via inner sources and boundary flux. We determine four kinds of simultaneous blow-up rates under different dominations of nonlinearities in the model. Two characteristic algebraic systems associated with the problem are introduced to get very simple descriptions for the four simultaneous blow-up rates as well as the known critical exponents, respectively. It is observed that the blow-up rates are independent of the nonlinear inner absorptions.

关键词： simultaneous blow-up rates asymptotic estimates characteristic algebraic system multicoupled parabolic system non-global solution critical exponent