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Accurate relocation of earthquakes in central-western China using the double-difference earthquake location algorithm

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Science China Earth Sciences 2003年第Z2期46卷 181-188页

作者： yANG Zhixian (杨智娴) CHEN yuntai (陈运泰) zheng yuejun (郑月军) yü Xiangwei (于湘伟) Institute of Geophysics China Seismological Bureau Beijing 100081 China Institute of Geophysics China Seismological Bureau Beijing 100081 China Institute of Crustal Dynamics China Seismological Bureau Beijing 100085 China Institute of Geophysics China Seismological Bureau Beijing 100081 China

The double-difference earthquake relocation algorithm (DD algorithm) has been applied to the accurate relocation of 10057 earthquakes in the central-western China (21°-36°N, 98°-112E°) during the period of 1992-1999. In total, 79706 readings for P waves and 72169 readings for S waves were used in the relocation, and the source parameters of 6496 events were obtained. The relocation results revealed a more complete picture of the hypocentral distribution in the central-western China. In several seismic belts the relocated epicenters present a more defined lineation feature, reflecting the close correlation between the seismicity and the active tectonic structures. The relocated focal depths confirmed that most earthquakes (91 percent of the 6496 relocated events) in the central-western China were located at shallower depths not deeper than 20 km. The distribution of focal depths indicates that the seismogenic layer in the central-western China is located in the upper-mid crust with its thickness no deeper than 20 km.

关键词： double-difference earthquake location, central-western China, earthquake relocation, seismogenic layer.

Nonlinear static and dynamic responses of an electrically actuated viscoelastic microbeam

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Acta Mechanica Sinica 2009年第2期25卷 211-218页

作者： y.M.Fu j.Zhang College of Mechanics and Aerospace Hunan University

On the basis of the Euler-Bernoulli hypothesis, nonlinear static and dynamic responses of a viscoelastic microbeam under two kinds of electric forces [a purely direct current （DC） and a combined current composed of a DC and an alternating current] are studied. By using Taylor series expansion, a governing equation of nonlinear integro-differential type is derived, and numerical analyses are performed. When a purely DC is applied, there exist an instantaneous pull-in voltage and a durable pull-in voltage of which the physical meanings are also given, whereas under an applied combined current, the effect of the element relaxation coefficient on the dynamic pull-in phenomenon is observed where the largest Lyapunov exponent is taken as a criterion for the dynamic pull-in instability of viscoelastic microbeams.

关键词： MEMS Viscoelastic microbeam Nonlineardynamics

B3 0749+460A: A New Repeat “Changing-look” Active Galactic Nucleus Associated with X-Ray Spectral Slope Variations

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Research in Astronomy and Astrophysics 2022年第1期22卷 114-125页

作者： j.Wang W.K.zheng D.W.Xu T.G.Brink A.V.Filippenko C.Gao S.S.Sun j.y.Wei Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and TechnologyGuangxi UniversityNanning 530004China Key Laboratory of Space Astronomy and Technology National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Department of Astronomy University of CaliforniaBerkeleyCA 94720-3411USA School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Miller Institute for Basic Research in Science University of CaliforniaBerkeleyCA 94720USA

Here we report an identification of B3 0749+460 A as a new double-peaked local "changing-look" active galactic nucleus(CL-AGN) in terms of our multi-epoch spectroscopic analysis. By comparing our new spectra taken in 2021 with the ones taken by the Sloan Digital Sky Survey in 2004, BOSS in 2013 and Ma NGA in 2016, we reveal type transitions of Seyfert(Sy) 1.9 → Sy1.8 → Sy1.9. In the transitions, the classical broad Hα emission fades away after 2013 and disappears in our 2021 spectrum, although the absence of broad Hβ can be traced back to at least 2016. A follow-up observation in X-rays by the Swift/XRT reveals that(1) the X-ray emission level gradually decreased since 2005;and(2)the X-ray spectrum is soft in the optical "turn-off" state and hard in the "turn-on" state. We argue that the disappearance of the classical broad Hα emission can be likely explained by the disk-wind broad-line-region model, in which the CL phenomenon is sensitive to luminosity in individual AGNs.

关键词： galaxies:Seyfert galaxies:nuclei (galaxies:)quasars:emission lines (galaxies:)quasars:individual(B30749+460A) X-rays:galaxies

A COMPREHENSIVE MODEL OF LASER CLADDING By POWDER FEEDING

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Acta Metallurgica Sinica(English Letters) 2004年第1期17卷 21-27页

作者： y.L.Huang G.y.Liang j.y.Su School of Materials Science and Engineering Xi'an Jiaotong University Xi'an 710049 ChinaSchool of Materials Science and Engineering Xi'an Jiaotong University Xi'an 710049 ChinaSchool of Materials Science and Engineering Xi'an Jiaotong University Xi'an 710049 China

A novel model was presented to predict the evolutionary development of cladding layer, and a method based on Lambert-Beer theorem and Mie's theory was adopted to treat the interaction between powder stream and laser beam. By using the continuum model and enthalpy-porosity method, the fluid flow and heat transfer in solid-liquid phase change system were simulated. The commercial software PHOENICS, to which several modules were appended, was used to accomplish the simulation. Numerical computation was performed for Stellite 6 cladding on steel, the obtained results are coincident with those measured in experiment basically.

关键词： laser cladding powder feeding cladding layer interaction

Spatial associations of tree species in a subtropical evergreen broad-leaved forest

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journal of Plant Ecology 2012年第3期5卷 346-355页

作者： zheng R.Luo Ming j.yu De L.Chen you G.Wu Bing y.Ding Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education and College of Life ScienceZhejiang UniversityHangzhou 310058China Management of Baishanzu Fengyangshan-Baishanzu National Nature ReserveQingyuan 323800China Department of Biology Science The School of Life and Environmental ScienceWenzhou UniversityWenzhou 325027China

Aims The spatial segregation hypothesis and the low-frequency hypothesis are two important proposed mechanisms that delay or prevent competitive exclusion in *** tree species interact with their neighbors,the importance of these potential processes can be investigated by analyzing the spatial structures of tree *** The distribution of the adults of 27 common tree species in a fully mapped 5-ha subtropical forest plot in Baishanzu,eastern China,was analyzed to investigate the community-level intra-and interspecific spatial association *** first tested for the overall spatial pattern in the 5-to 40-m neighborhoods and classified first-order bivariate associations with a diametric scheme based on Ripley’s K and nearest-neighbor statistic(G-function).Then heterogeneous Poisson null models were used to distinguish second-order interactions from overall spatial associations(including first-order effects).Finally,we analyzed correlations between the existence of species interactions and some attributes of the species *** Findings Partial overlap and segregation increased with scale,whereas mixing *** 70%of the species pairs occurred less than expected at random,and only 3.4%of the species pairs were well mixed;11.0%of all species pairs showed significant small-scale interactions,which was a greater frequency than expected by chance if species are abundant or prefer the same habitat,but less frequent than expected if species are highly *** suggests that both spatial segregation and low frequency of species facilitate species coexistence by reducing the opportunity that trees of two species encounter each *** study also revealed that positive interactions were more prevalent than negative interactions in the forest,which indicates that positive interactions may have important effects on forest species assemblies.

关键词： Baishanzu point pattern analysis spatial segregation low frequency interaction opportunity

Dual effect of Cu on the Al3Sc nanoprecipitate coarsening

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journal of Materials Science & Technology 2020年第2期37卷 38-45页

作者： y.H.Gao L.F.Cao j.Kuang j.y.Zhang G.Liu j.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an710049China International joint Laboratory for Light Alloys(Ministry of Education) Chongqing UniversityChongqing 400044China

It is generally considered that the Al3Sc nanoprecipitates are highly thermal stable,mainly due to quite slow Sc diffusion in theα-Al *** this paper,we demonstrate in an Al-Cu-Sc alloy that the Cu atoms have dual effect on the coarsening of Al3Sc *** the one hand,the Cu atoms with high diffusivity tend to accelerate the Al3Sc coarsening,which results from the Cu-promoted Sc *** the other hand,some Cu atoms will segregate at the Al3Sc/matrix interface,which further stabilizes the Al3Sc nanoprecipitates by reducing the interfacial *** between these two effects is tailored by temperature,which rationalizes the experimental findings that the coarsening kinetics of Al3Sc nanoprecipitate is greatly boosted at 300℃-overaging while significantly suppressed at 400℃-overaging.

关键词： Al alloys Precipitate coarsening Interfacial segregation Microstructural evolution

Multi-relaxation-time lattice Boltzmann simulations of lid driven flows using graphics processing unit

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Applied Mathematics and Mechanics(English Edition) 2017年第5期38卷 707-722页

作者： Chenggong LI j.P.y.MAA National Engineering Laboratory for Methanol to Olefins Dalian National Laboratory for Clean EnergyDalian Institute of Chemical PhysicsChinese Academy of Sciences College of William and Mary Virginia Institute of Marine Science

Large eddy simulation （LES） using the Smagorinsky eddy viscosity model is added to the two-dimensional nine velocity components （D2Q9） lattice Boltzmann equation （LBE） with multi-relaxation-time （MRT） to simulate incompressible turbulent cavity flows with the Reynolds numbers up to 1 × 10^7. To improve the computation efficiency of LBM on the numerical simulations of turbulent flows, the massively parallel computing power from a graphic processing unit （GPU） with a computing unified device architecture （CUDA） is introduced into the MRT-LBE-LES model. The model performs well, compared with the results from others, with an increase of 76 times in computation efficiency. It appears that the higher the Reynolds numbers is, the smaller the Smagorinsky constant should be, if the lattice number is fixed. Also, for a selected high Reynolds number and a selected proper Smagorinsky constant, there is a minimum requirement for the lattice number so that the Smagorinsky eddy viscosity will not be excessively large.

关键词： large eddy simulation (LES) multi-relaxation-time (MRT) lattice Boltzmann equation (LBE) two-dimensional nine velocity components (D2Q9) Smagorinskymodel graphic processing unit (GPU) computing unified device architecture (CUDA)

Motion of the moonlet in the binary system 243 Ida

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Acta Mechanica Sinica 2018年第1期34卷 214-224页

作者： L.Lan y.Ni y.jiang j.Li School of Aerospace Engineering Tsinghua University State Key Laboratory of Astronautic Dynamic Xi'an Satellite Control Center

The motion of the moonlet Dactyl in the binary system 243 Ida is investigated in this paper. First, periodic orbits in the vicinity of the primary are calculated, including the orbits around the equilibrium points and large-scale orbits. The Floquet multipliers’ topological cases of periodic orbits are calculated to study the orbits’ stabilities. During the continuation of the retrograde near-circular orbits near the equatorial plane, two period-doubling bifurcations and one Neimark–Sacker bifurcation occur one by one, leading to two stable regions and two unstable regions. Bifurcations occur at the boundaries of these regions. Periodic orbits in the stable regions are all stable, but in the unstable regions are all unstable. Moreover, many quasi-periodic orbits exist near the equatorial plane. Long-term integration indicates that a particle in a quasi-periodic orbit runs in a space like a tire. Quasi-periodic orbits in different regions have different styles of motion indicated by the Poincare sections. There is the possibility that moonlet Dactyl is in a quasi-periodic orbit near the stable region I, which is enlightening for the stability of the binary system.

关键词： Binary system Bifurcation Periodic orbits Quasi-periodic orbits

Nanocrystalline Silicon Thin Films Fabricated at 80℃ by Using Electron Cyclotron Resonance Chemical Vapor Deposition

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Plasma Science and Technology 2010年第5期12卷 608-613页

作者： I.y.y.BU A.j.FLEWITT W.I.MILINE Department of Microelectronics Engineering National Kaohsiung Marine University Electrical Engineering Division Engineering Department Cambridge University

Deposition of nanocrystalline silicon （nc-Si） on glass at very low temperatures by electron cyclotron resonance （ECR） plasma enhanced chemical vapour deposition （PECVD） was investigated. It was shown that nc-Si could be deposited from hydrogen diluted silane gas at a substrate temperature of 80℃ with a crystalline fraction up to 80% and a lateral grain size of around 50 nm. This was achieved by growing the nc-Si in a low pressure regime which ensured that mono-silyl species were the dominant deposition precursor. Furthermore, a high flux of energetic hydrogen ions was required to induce crystallisation of the silicon material through a chemical annealing process.

关键词： low temperature nanocrystalline silicon ECR