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Misorientation dependent thermal condition-solute field cooperative effect on competitive grain growth in the converging case during directional solidification of a nickel-base superalloy

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Journal of materials science & Technology 2022年第1期96卷 151-159页

作者： X.B.Meng J.G.Li C.N.Jing J.D.Liu s.y.ma J.J.Liang C.W.Zhang M.Wang B.T.Tang T.Lin J.L.Chen X.L.Zhang Q.Li school of Mechanical and Automotive Engineering Qilu University of Technology(Shandong Academy of Sciences)Jinan 250353China Institute of Metal Research Chinese Academy of SciencesShenyang110016China school of materials science and Engineering Shandong Jianzhu UniversityJinan 250014China AECC shenyang Liming Aero-Engine Co. LTD.Shenyang110043China College of material science and Engineering North Minzu UniversityYinchuan 750021China Faculty of electro-mechanical information Weifang University of Science and TechnologyShouguang262700China

Nowadays,thermal condition and solute field are considered as the potential dominant factors controlling competitive grain growth during directional solidification process.However,the controlling modes and critical conditions of competitive grain growth have been drastically debated over the past two decades.In this work,thermal condition and solute field are combined to study the competitive grain growth in the converging case by experimental observation and numerical simulation of bicrystal samples.We find the competitive grain growth is controlled by the cooperative effect of thermal condition and solute field,and the controlling modes are related to the bicrystal misorientation between favorably and unfavorably oriented grains.When the unfavorably oriented grain is low misoriented,unfavorably oriented grain dominates grain selection,and the competitive grain growth performs as solute field domination.However,with the increase of unfavorably oriented grain’s misorientation,the grain selection converts into favorably oriented grain domination,and the competitive grain growth changes to thermal condition domination.To explain these abnormal transformation phenomena,we propose a misorientation dependent thermal condition-solute field cooperative domination model and identify the critical conditions by a critical misorientation(θ_(cm)).According to dynamic equation of dendrite growth,we calculate the critical misorientationθ;to prove this model.The theoretical calculation results agree well with the experimental results.

关键词： Competitive grain growth Cooperative effect Thermal condition solute field Critical misorientation Unusual overgrowth Abnormal transformation

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GLOBAL IONOsPHERIC REsPONsE TO THE maGNETIC sTORM OF OCTOBER 1989

GLOBAL IONOSPHERIC RESPONSE TO THE MAGNETIC STORM OF OCTOBER...

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1993 International symposium on Radio Propagation(IsRP’93)

作者： s.y.ma K.C.yeh Dept.of space Physics Wuhan University Dept.of ECE University of IllinoisUrbanaIL 61801USA

＜正＞Using the data from 40 ionosonde stations and 12 TEC stations,a study is made on the global behavior of ionospheric response to the magnetic storm of October 1989.

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seasonal variation of the ion upflow in the topside ionosphere during subauroral Polarization streams periods

Seasonal variation of the ion upflow in the topside ionosphe...

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中国空间科学学会空间物理学专业委员会第十五届全国日地空...

作者： H.Wang s.y.ma H.Luehr Dept.of space Physics School of Electronic InformationWuhan University Helmholtz Centre Potsdam-GFZ German Research Center for GeosciencesD-14473 PotsdamGermany

A statistical study has been performed by using two years of DMsP plasma observations to investigate the seasonal effect of sAPs（subauroral Polarization streams）on the ion upflow in the duskside ionosphere in the Northern Hemisphere.There are obvious upflows occurring in the topside ionosphere around the sAPs region,exceeding 200 m/s at winter solstice,indicating the important effect of sAPs on the local plasma upward motion.Both sAPs and ion upward velocity show similar seasonal variations,largest in winter and smallest in summer,irrespective of geomagnetic activities.A good correlation is found and a linear relationship is derived between sAPs and the ion upflow velocity.The ion temperature drops down around the sAPs region,which can be explained by the cooler gas ahead of the upwelling hot ion gas due to the frictional heating.The electron temperature elevates around the sAPs region due to the energy input from the inner magnetosphere.Both the ion and electron temperatures are higher in summer than in winter,except for Kp≥4 when the winter and summer electron temperatures are quite comparable.The present work highlights the important role of the sAPs related frictional heating at mid latitudes in the local formation of the strong upward flow,which might provide a direct ionospheric ion source for the plasmasphere in the duskside subauroral region.

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A study on Equatorial Ionization Anomaly——CHAMP and GRACE observations

A study on Equatorial Ionization Anomaly——CHAMP and GRACE ...

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中国空间科学学会空间物理学专业委员会第十五届全国日地空...

作者： C.Xiong s.y.ma H.Lühr Helmholtz Centre Potsdam GFZ German Research Centre for GeosciencesTelegrafenberg14473 PotsdamGermany Department of space Physics College of Electronic InformationWuhan University

Based on nearly nine years（2001-2009）of observations from CHAMP and GRACE,a comprehensive study of the equatorial ionization anomaly（EIA）is presented,which mainly focus on the seasonal and local time variation,as well as the tidal signatures of the EIA magnitude and inter-hemisphere asymmetry.The electron density and the magnetic latitude of the EIA crest both peak around 1400LT while the crest-to-trough ratio（CTR）of the EIA reaches its highest value post-sunset around 2000LT,with a value almost twice the daytime level.During solstice seasons a clear inter-hemispheric asymmetry of the EIA can be seen.At CHAMP altitude the electron density of the EIA crest is stronger in the winter hemisphere during morning to noontime hours and reverses to the summer hemisphere after noontime,while at GRACE altitude the electron density of the EIA crest is always stronger in the summer hemisphere over the whole daytime.simulation results from the sAMI2 model also show the differences in EIA inter-hemisphere asymmetry at the two altitudes.For the tidal signatures,the EIA magnitude parameters show longitudinal wavenumber 4 and 3（WN4/WN3）patterns during the months around August/December solstice,respectively.While for different parameters the contributions of the tides are different.For the CTR,the leading tidal component contribute to WN4 is DE3 during the months around August,while during the months around December solstice the stationary planetary wave,sPW3,takes a comparable role as DE2 in contributing to WN3.For the apex height of the fluxtube（ApexHC）,the stationary planetary wave,sPW4/sPW3 exceeds the amplitudes of DE3/DE2 taking the leading role for the longitudinal WN4/WN3 patterns.During the months around December solstice the sW3 tide is prominent in both CTR and ApexHC.sW3 shows high dependence on solar flux,while it is almost independent on magnetic activity.

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simultaneous observations of large-scale traveling ionospheric disturbances on the nightside and dayside middle latitude

Simultaneous observations of large-scale traveling ionospher...

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中国空间科学学会空间物理学专业委员会第十五届全国日地空...

作者： H.T.Cai F.yin s.y.ma J.s.Xu y.W.Liu Department of space Physics School of Electronic InformationWuhan University Key Laboratory of Geospace Environment and Geodesy Ministry of Education of PRC

In this paper,we present further observational evidences for the trans-polar propagation of Large-scale Traveling Ionospheric Disturbances(LsTIDs)from their nightside source region to the dayside reported by Cai et al.(2011).slant Total Electron Content(sTEC)observed by longitudinally-aligned GPs receiver chains in North American and European sectors were analyzed to demonstrate presences of LsTIDs at both nightside and dayside mid-latitude.signatures of TID were inferred from phase difference in time series of sTEC perturbations(TECP)derived from measurements of ground-based GPs receivers,which are separated by hundreds kilometer longitudinally.Periods of the day-time and night-time ionospheric disturbances were estimated to be around 128 minutes,being in good agreement with that of the trans-polar AGW recorded by EIsCAT/EsR radars.On the dayside,the LsTID moved equatorward with an average phase speed of40 m/s.In North American sector,however,southward speed of the night-time LsTID was much slower,being around 160 m/s.We suggest that the observed day-time and night-time mid-latitude LsTIDs are likely to have the same source region,being located somewhere at night-time auroral latitude.Having been launched on the nightside,the waves propagate simultaneously equatorward and poleward.The equatorward moving waves are recorded by GPs receiver chain in North American sector.The poleward-moving waves,however,cross the polar cap from nightside to dayside and then are detected consecutively at high-and mid-latitudes by EIsCAT/EsR radars and GPs receiver chains,respectively.

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Ion distributions in RC retrieved from TWINs ENA by differential voxel CT technique

Ion distributions in RC retrieved from TWINS ENA by differen...

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中国空间科学学会空间物理学专业委员会第十五届全国日地空...

作者： s.y.ma W.N.yan L.Xu J.Goldstein D.J.McComas Dept.of space Physics College of Electronic InformationWuhan University southwest Research Institute 6220 Culebra RoadSan AntonioTX 78238-5166USA

The Two Wide-angle Imaging Neutral-atom spectrometers(TWINs)mission of NAsA is the first constellation to carry out stereoscopic magnetospheric imaging of energetic neutral atoms(ENA)from a twain of spacecrafts flying on two widely-separated Molniya orbits.It provides unique opportunity to retrieve the 3-D distribution of ions in the ring currents(RC)by using volumetric pixel(voxel)CT inversion method.In this study the voxel CT method is implemented for a series of differential ENA fluxes averaged over about 6 sweeps(corresponding to a time period of min.)at different energy levels ranging from 5 to 100 keV obtained during the main phase of a great magnetic storm with min.sym-H of-156 nT on October 24-25,2011.The data were selected to span a period about 50 minutes during which a large substorm was undergoing its expansion phase first and then recovery.The ENA species of O and H are distinguished by analyzing the signals of pulse height of second electrons emitted from the carbon foil and impacted on the MCP detector in the TWINs sensors.To eliminate the possible instrument bias error,a differential voxel CT technique is applied.The flux intensity of the ENAs’parent ions in the ring current(RC)has been obtained as a function of energy,L value,MLT sector and latitude,along with their time evolution during the storm-time substorm expansion phase.It shows that the RC is highly asymmetry with major part in the midnight to dawn sector for equatorial latitudes.At the midway of the substorm expansion there occurred a sudden large enhancement of equatorial ion flux at lower energy of 5 keV in the dusk sector with narrow extent less than 2 hours near the synchronous orbit of 5.5 Re.The ion flux spectra underwent dramatic changes.At the expansion maximum of the substorm,the spectra show a single peak at higher energy0 keV.For the midway of the expansion there are two peaks at higher and lowest energies,showing a valley at0 keV where the quiet time spectra have their peak and begin to roll down quickly.

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区域地震滑坡体积优化模型

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世界地震译丛 2018年第3期49卷 287-299页

作者： C.Xu X.W.Xu L.L.shen Q.yao X.B.Tan W.J.Kang s.y.ma X.y.Wu J.T.Cai M.X.Gao K.Li 许冲(译) 吕春来(校) 不详中国地震局地质研究所中国地震局地球物理研究所

求取滑坡体积在当前是一个难题,原因是其为三维分量,并且部分滑面往往在地下。本文提出了3个区域地震滑坡体积优化模型来计算2008年中国汶川M W7.9地震触发滑坡的体积。本文首先基于20m分辨率的震前和震后sPOT 5卫星影像提取到的数字高... 详细信息

求取滑坡体积在当前是一个难题,原因是其为三维分量,并且部分滑面往往在地下。本文提出了3个区域地震滑坡体积优化模型来计算2008年中国汶川M W7.9地震触发滑坡的体积。本文首先基于20m分辨率的震前和震后sPOT 5卫星影像提取到的数字高程模型(DEM)数据,结合少数滑坡的剖面图,获得了1 415处汶川地震滑坡堆积区体积,作为地震滑坡体积模型训练样本。在常规区域滑坡"体积—面积"模型基础上,提出了3个优化模型。分别利用数据的对数化线性拟合与直接非线性拟合方法对1个常规模型和3个优化模型进行拟合。结果表明,采用直接非线性拟合方法并考虑了滑坡长、宽、高、岩性、坡度和峰值地动加速度后,坡向的优化模型标准误差最小,回归得到的滑坡总体积与滑坡真实总体积也非常接近。将这一模型应用于所有汶川地震滑坡,分别得到每个滑坡的体积。最终结果表明,汶川地震滑坡相对密集分布区内的196 007处滑坡的堆积物体积约为1.2×1010 m^3,源区体积约为1×1010 m^3。根据前人"地震震级—滑坡总体积"经验公式得到的结果仅仅是本文结果的7.5%~9%,这提醒我们有必要基于更多的单次地震触发滑坡总体体积数据对"地震震级—滑坡总体积"的关系进行更新。同时,文中的优化模型对同类研究也有显著的参考价值。

关键词：地震滑坡体积模型优化模型数字高程模型拟合方法地震触发地震震级 sPOT

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Ren-integrable and ren-symmetric integrable systems

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Communications in Theoretical Physics 2024年第3期76卷 62-69页

作者： s y Lou school of Physical science and Technology Ningbo UniversityNingbo315211China

A new type of symmetry,ren-symmetry,describing anyon physics and corresponding topological physics,is proposed.Ren-symmetry is a generalization of super-symmetry which is widely applied in super-symmetric physics such as super-symmetric quantum mechanics,super-symmetric gravity,super-symmetric string theory,super-symmetric integrable systems and so on.supersymmetry and Grassmann numbers are,in some sense,dual conceptions,and it turns out that these conceptions coincide for the ren situation,that is,a similar conception of ren-number(R-number)is devised for ren-symmetry.In particular,some basic results of the R-number and ren-symmetry are exposed which allow one to derive,in principle,some new types of integrable systems including ren-integrable models and ren-symmetric integrable systems.Training examples of ren-integrable KdV-type systems and ren-symmetric KdV equations are explicitly given.

关键词： symmetries integrable systems anyon physics extended supersymmetry ren-symmetry

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Effect of Eu3+,Bi3+,and Li+ doping on luminescent property of GdNbO4

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Journal of Rare Earths 2024年第1期42卷 66-75页

作者： s.W.Wi y.s.Lee Department of Physics and Integrative Institute of Basic sciences Soongsil University

We investigated the emission properties of Eu3+-doped GdNbO4-based oxide phosphors,aiming at improving the Eu3+emission by codoping of Bi3+and Li+.Eu3+singly doped,Eu3+and Bi3+doubly doped,and Eu3+,Bi3+,and Li+triply doped GdNbO4were prepared using a high-temperature solid-state reaction method.The red-orange emissions from Eu3+in the singly doped samples are significantly improved by the codoping of Bi3+,mainly due to the energy transfer from Bi3+to Eu3+.The additional codoping of Li+is found to increase the Eu3+emission significantly.This improvement might be attributed to the increase in the photoluminescent quantum yield originating from larger grain sizes and better crystallinity.A detailed analysis of the X-ray diffraction pattern and the asymmetric ratio estimated from the photoluminescence spectra show that the local lattice environment around Eu3+in GdNbO4does not change significantly with the codoping of Bi3+and Li+.Our results indicate that Li+doping is a promising way to improve the emission properties of rare-earth ion-doped GdNbO4phosphors.

关键词： Eu 3+ GdNbO 4 Codoping of Li + Photoluminescence sensitizer Rare earths

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Construction of 2D/2D Ti_(3)C_(2)T_(x)MXene/Cds heterojunction with photothermal effect for efficient photocatalytic hydrogen production

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Journal of materials science & Technology 2024年第4期171卷 1-9页

作者： T.y.Huang Z.yang s.y.yang Z.H.Dai y.J.Liu J.H.Liao G.y.Zhong Z.J.Xie y.P.Fang s.s.Zhang Key Laboratory for Biobased materials and Energy of Ministry of Education Guangdong Laboratory for Lingnan Modern AgricultureCollege of Materials and EnergySouth China Agricultural UniversityGuangzhou 510643China school of Physics and Optoelectronics South China University of TechnologyGuangzhou 510640China school of Chemical Engineering and Energy Technology Guangdong Provincial Key Laboratory of Distributed Energy SystemsDongguan University of TechnologyDongguan 523808China

The insensitivity of semiconductors to visible and infrared light is a key constraint on the utilization of light energy in photocatalytic reactions.Constructing photocatalysts with full-spectrum absorption through surface engineering is an effective approach to fully harnessing light energy in semiconductor materials.Herein,a novel stable Ti_(3)C_(2)T_(x)MXene/Cds heterojunction catalyst is obtained by in-situ epitaxial growth of two-dimensional(2D)Cds nanosheets on 2D MXene interface via a solvothermal method.The exceptional light absorption properties of MXene confer outstanding full-spectrum driven photocat-alytic hydrogen evolution capability upon the heterogeneous catalyst.The unique 2D/2D structure effectively mitigated the recombination of photogenerated carriers,enhancing the photocatalytic performance of the catalyst.Moreover,the composite catalyst exhibits a significantly higher surface temperature of 80.4℃under visible light irradiation at an intensity of 0.1 W/cm^(2),which is 1.84 times higher than that of Cds.Under irradiation of visible and near infrared light,the composite catalyst with photothermal ef-fect demonstrates a remarkable hydrogen evolution rate of 65.4 mmol g^(-1)h^(-1),which is 7.2 times higher than that of Cds catalyst.This study introduces a novel approach for constructing full-spectrum absorption catalysts and expands the application of the photothermal effect in photocatalytic hydrogen evolution research.

关键词： Two-dimensional structure Heterostructure Photothermal effect Photocatalyst Hydrogen evolution

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