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Discovery of high-velocity EHB stars in the globular cluster ωCentauri(NGC 5139)

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Research in Astronomy and Astrophysics 2015年第10期15卷 1639-1646页

作者： xin-hua Gao Shou-Kun Xu Li chen School of Information Science and Engineering Changzhou University Shanghai Astronomical Observatory Chinese Academy of Sciences

Abstract We report the discovery of 45 high-velocity extreme horizontal branch （EHB） stars in the globular cluster Omega Centauri （NGC 5139）. The tangential ve- locities of these EHB stars are determined to be in the range 93-313 km s^-1, with an average uncertainty of -27 km s^-1. The central escape velocity of the cluster is determined to be in the range 60~105 km s^-1. These EHB stars are significantly more concentrated toward the cluster core compared with other cluster members. The formation mechanisms of these EHB stars are discussed. Our conclusions can be sum- marized as follows：（1） A comparison of the tangential velocities of these EHB stars to the central escape velocity of the cluster shows that most if not all of these EHB stars are unbound to the cluster; （2） These EHB stars obtained high velocities in the central cluster region no longer than - 1 Myr ago and may be subsequently ejected from the cluster in the next -1 Myr; （3） If the progenitors of these EHB stars were single stars, then they may have experienced a fast mass-loss process. If the progen- itors were in close binaries, then they may have formed through disruptions by the intermediate-mass black hole in the cluster center.

关键词： Galaxy: globular clusters: individual: ω Cen (NGC 5139) -- stars:Hertzsprung-Russell and C-M diagrams -- stars: kinematics and dynamics -- stars:binaries (including multiple): close

Enthalpies Estimation of Formation of Monosubstituted Alkanes by Interaction Potential Index

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Chinese Journal of Chemical Physics 2012年第2期25卷 153-160,I0003页

作者： Ya-xin Wu chen-zhong Cao hua Yuan School of Chemistry and Chemical Engineering Central South UniversityChangsha 410083China School of Chemistry and Chemical Engineering Key Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of EducationHunan University of Science and Technologyand Hunan Provincial University Key Laboratory of QSAR/QSPRXiangtan 411201China

The interaction potential index IPI（X） of 16 Br, C1, I, NO2, CN, CHO, COOH, CH3, CH： kinds of substituents X （X---OH, SH, NH2, ：CH2, C-CH, Ph, COCH3, COOCH3） were proposed, which are derived from the experimental enthalpies of formation △fHФ （g） values of monosubstituted straight-chain alkanes. Based on the IPI（X） and polarizability effect index, a simple and effective model was constructed to estimate the △fHФ （g） values of monosubstituted alkanes RX （including the branched derivatives）. The present model takes into account not only the contributions of the alkyl R and the substituent X, but also the contribution of the interaction between R and X. Its stability and prediction ability was confirmed by the results of leave-one-out method. Compared with previous reported studies, the obtained equation can be used to estimate enthalpies of formation for much more kinds of monosubstituted alkanes with less parameters. Thus, it is recommended for the calculation of the △fHФ（g） for the RX.

关键词： Interaction potential index Substituent Monosubstituted alkane Enthalpy offormation Polarizability effect index

Multiplicity of solutions for the semilinear subelliptic Dirichlet problem

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Science China Mathematics 2024年第3期67卷 475-504页

作者： hua chen Hong-Ge chen Jin-Ning Li xin Liao School of Mathematics and Statistics Wuhan UniversityWuhan 430072China Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430071China

In this paper,we study the semilinear subelliptic equation{−△Xu=f(x,u)+g(x,u)inΩ,u=0 on∂Ω,where△X=−∑m i=1 Xi∗Xi is the self-adjoint Hormander operator associated with the vector fields X=(X_(1),X_(2),...,X_(m))satisfying the Hormander's condition,f(x,u)∈C(Ω×R),g(x,u)is a Carathéodory function onΩ×R,andΩis an open bounded domain in R~n with smooth *** the perturbation from the symmetry method with the approaches involving the eigenvalue estimate and the Morse index in estimating the minimax values,we obtain two kinds of existence results for multiple weak solutions to the problem ***,we discuss the difference between the eigenvalue estimate approach and the Morse index approach in degenerate *** with the classical elliptic cases,both approaches here have their own strengths in the degenerate *** new phenomenon implies that the results in general degenerate cases would be quite different from the situations in classical elliptic cases.

关键词： degenerate elliptic equations Hormander operators perturbation method Morse index

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3D cluster members and near-infrared distance of open cluster NGC 6819

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Research in Astronomy and Astrophysics 2015年第12期15卷 2193-2203页

作者： xin-hua Gao Shou-Kun Xu Li chen School of Information Science and Engineering Changzhou University Shanghai Astronomical Observatory Chinese Academy of Sciences

In order to obtain clean members of the open cluster NGC 6819, the proper motions and radial velocities of 1691 stars are used to construct a three-dimensional （3D） velocity space. Based on the DBSCAN clustering algorithm, 537 3D cluster members are obtained. From the 537 3D cluster members, the average radial velocity and absolute proper motion of the cluster are Vr = ＋2.30 ±0.04 km s-1 and （PMRA, PMDec） = （-2.5 ±0.5, -4.3 ± 0.5） mas yr-1, respectively. The proper motions, radial velocities, spatial positions and color-magnitude diagram of the 537 3D members indicate that our membership determination is effective. Among the 537 3D cluster members, 15 red clump giants can be easily identified by eye and are used as reliable standard candles for the distance estimate of the cluster. The distance modulus of the cluster is determined to be （m - M）0 -- 11.86 ± 0.05 mag （2355 ±54 pc）, which is quite consistent with published values. The uncertainty of our distance mod- ulus is dominated by the intrinsic dispersion in the luminosities of red clump giants （--0.04 mag）.

关键词： open clusters and associations: individual (NGC 6819) -- Hertzsprung-Russell and C-M diagrams -- stars: kinematics and dynamics -- stars: distances

Microstructures and Mechanical Properties of Helical Bevel Gears Made by Mn-Cu Alloyed Austempered Ductile Iron

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Journal of Iron and Steel Research International 2012年第2期19卷 36-42页

作者： LIU Sheng-fa chen Yang chen xin MIAO hua-ming School of Materials Science and Engineering Wuhan University of Technology Wuhan 430070 Hubei China

Austempered ductile iron （ADI） has several advantages of replacing cast steel and forged steel in many engineering fields. A new Mn-Cu alloyed ADI with excellent mechanical properties has been developed in order to cut the cost and enlarge the application of ADI. The helical bevel gears were made of the new-developed Mn-Cu alloyed ADI. The microstructure and mechanical properties of the standard sample were investigated by optical microscope （OM）, scanning electron microscope （SEM） and performance measurement. The results showed that after a series of treatments, the mechanical properties （Rm 1007. 4 to 1200 MPa, A 5.2% to 8. 8%, HRC 32 to HRC 35, O^K 70 to 120 J/cmz ） of the Mn-Cu alloyed ADI standard sample could reach European standard EN1564-97/ EN-CJS-1000-5. The surface hardness after helical bevel gears meshing was significantly increased due to the formation of martensite. The bench test and traffic running testing results suggested that the new Mn-Cu alloyed ADI with ultimate life and median life respectively exceeding 30×104 and 50 × 10^4 times could replace 20CrMnTi forged steel for manufacturing the EQ140 helical bevel gears.

关键词： ADI Mn mechanical property helical bevel gear

Shape Optimization for A Conventional Underwater Glider to Decrease Average Periodic Resistance

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China Ocean Engineering 2021年第5期35卷 724-735页

作者： LI Jing-lu WANG xin-jing WANG Peng DONG hua-chao chen Cai-hua School of Marine Science and Technology Northwestern Polytechnical UniversityXi’an 710072China

As a type of autonomous underwater vehicle(AUV),underwater gliders(UG)are getting increasing attention in ocean *** save energy and satisfy the mission requirements of a longer voyage,shape optimization for UGs has become a key technique and research *** this paper,a conventional UG,including its fuselage and hydrofoil,is optimized,which aims to decrease the average resistance in one motion *** operate the optimization progress for the complex object,multiple free form deformation(FFD)volumes are established for geometric ***-fidelity simulation models are employed for objective function evaluation and gradients *** sequential quadratic programming(SQP)method is adopted as an optimization *** optimization results show that there exists a UG with symmetrical and non-horizontal hydrofoils that has lower resistance.

关键词： underwater glider shape optimization conventional configuration free form deformation

The Gevrey smoothing effect for the spatially inhomogeneous Boltzmann equations without cut-off

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Science China Mathematics 2022年第3期65卷 443-470页

作者： hua chen xin Hu Wei-Xi Li Jinpeng Zhan School of Mathematics and Statistics Wuhan UniversityWuhan 430072China Computational Science Hubei Key Laboratory Wuhan UniversityWuhan 430072China Department of Mathematics School of ScienceWuhan University of TechnologyWuhan 430070China

In this article we study the Gevrey regularization effect for the spatially inhomogeneous Boltzmann equation without angular *** equation is partially elliptic in the velocity direction and degenerates in the spatial *** consider the nonlinear Cauchy problem for the fluctuation around the Maxwellian distribution and prove that any solution with mild regularity will become smooth in the Gevrey class at positive time with the Gevrey index depending on the angular *** proof relies on the symbolic calculus for the collision operator and the global subelliptic estimate for the Cauchy problem of the linearized Boltzmann operator.

关键词： Boltzmann equation Gevrey regularity subelliptic estimate non cut-off symbolic calculus

Lethaclado acid A and B from Lethariella cladonioides

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Chinese Chemical Letters 2007年第12期18卷 1515-1517页

作者： xin huang Jun Li Jian hua Shen Jun hua chen Drug Discovery and Design Centre State Key Laboratory of Drug Research Shanghai Institute of Materia Medica Shanghai Institutes for Biological Sciences Chinese Academy of Sciences Shanghai 201203 PR China

Two new compounds, lethaclado acid A （1） and B （2）, were isolated from the acetone extract ofLethariella cladonioides. Their structures were elucidated on the basis of 1D and 2D NMR as well as ESI-MS spectral data.

关键词： Lethariella cladonioides Depside Depsidone Lethaclado acid A Lethaclado acid B

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正交设计在观赏石斛种胚离体培养中的应用

广西林业科学 2016年第3期45卷 306-310页

作者：龚建英王华新陈宝玲陈尔杨舒婷苏莉花广西壮族自治区林业科学研究院南宁530002

利用正交设计方法 L9（34）,研究石斛种类、MS用量、有机添加物种类以及6-BA浓度等4个因子对观赏石斛种胚离体培养的影响,结果表明：6-BA浓度是影响观赏石斛种胚萌动时间的主要因子,其次是石斛种类,最后是有机添加物种类和MS用量。观赏... 详细信息

利用正交设计方法 L9（34）,研究石斛种类、MS用量、有机添加物种类以及6-BA浓度等4个因子对观赏石斛种胚离体培养的影响,结果表明：6-BA浓度是影响观赏石斛种胚萌动时间的主要因子,其次是石斛种类,最后是有机添加物种类和MS用量。观赏石斛种胚萌动最优的水平组合为金钗石斛＋MS＋香蕉＋6-BA0.2 mg/L,种胚最快萌动时间为9.6 d。MS用量和6-BA浓度是影响观赏石斛种胚萌发率的主要因子,其次是有机添加物种类,最后是石斛种类。观赏石斛种胚萌发率最优的水平组合为重唇石斛＋MS＋土豆＋6-BA 0.2mg/L,种胚萌发率达100%。

关键词：观赏石斛种胚培养正交设计