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Modeling the Newtonian dy.amics for rotation curve analy.is of thin-disk galaxies

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Research in Astronomy.and Astrophy.ics 2011年第12期11卷 1429-1448页

作者： James q.feng C.F.Gallo Superconix Inc 2440 Lisbon AvenueLake ElmoMN 55042USA

We present an efficient, robust computational method for modeling the Newtonian dy.amics for rotation curve analy.is of thin-disk galaxies. With appropriate mathematical treatments, the apparent numerical difficulties associated with singularities in computing elliptic integrals are completely.removed. Using a boundary.element discretization procedure, the governing eq.ations are transformed into a linear algebra matrix eq.ation that can be solved by.straightforward Gauss elimination in one step without further iterations. The numerical code implemented according to our algorithm can accurately.determine the surface mass density.distribution in a disk galaxy.from a measured rotation curve （or vice versa）. For a disk galaxy.with a ty.ical flat rotation curve, our modeling results show that the surface mass density.monotonically.decreases from the galactic center toward the periphery. according to Newtonian dy.amics. In a large portion of the galaxy. the surface mass density.follows an approximately.exponential law of decay.with respect to the galactic radial coordinate. y.t the radial scale length for the surface mass density.seems to be generally.larger than that of the measured brightness distribution, suggesting an increasing mass-tolight ratio with the radial distance in a disk galaxy. In a nondimensionalized form, our mathematical sy.tem contains a dimensionless parameter which we call the ＂galactic rotation number＂ that represents the gross ratio of centrifugal force and gravitational force. The value of this galactic rotation number is determined as part of the numerial solution. Through a sy.tematic computational analy.is, we have illustrated that the galactic rotation number remains within 4-10% of 1.70 for a wide variety.of rotation curves. This implies that the total mass in a disk galaxy.is proportional to V02 Rg, with V0 denoting the characteristic rotation velocity.（such as the ＂flat＂ value in a ty.ical ro- tation curve） and Rg the radius of the galacti

关键词： galaxy. disk -- galaxies: general -- galaxies: kinematics and dy.amics -- galaxies: structure -- methods: numerical and analy.ical

q.ANTITATIVE ANALy.IC TECHNOLOGy.OF ULTRA-HARDNESS AND WEAR RESISTENT SURFACING MATERIAL

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Acta Metallurgica Sinica(English Letters) 2004年第1期17卷 28-32页

作者： W.S.Li B.S.Wang L.Z.feng y.q.Zhou y.M.Zhang School of Matericals Science and Engineering Tianjin University Tianjin 300072 ChinaSchool of Matericals Science and Engineering Tianjin University Tianjin 300072 ChinaSchool of Matericals Science and Engineering Tianjin University Tianjin 300072 ChinaSchool of Matericals Science and Engineering Tianjin University Tianjin 300072 ChinaSchool of Matericals Science and Engineering Tianjin University Tianjin 300072 China

Mathematical models between surfacing welding properties of C, Cr, Mo, V, W alloy.sy.tem and encode factors of alloy.additives are established by.test methods of advanced trial optimizing technology.and computer assistant design (CAD). They.help to draw unitary.functions and binary.isoclines diagrams through which the influence of encode factorial linearity. nonlinear effect and factors interaction of alloy.additives on the performances of surfacing welding can be analy.ed directly.and q.antitatively. Meanwhile, the performances of deposited metal can also be predicted according to the content of alloy.additives.

关键词： surfacing materials ultra-high hardness wear resistant q.antitative analy.is

Mechanical properties of cocoons constructed consecutively.by.a single silkworm caterpillar,Bomby. mori

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Acta Mechanica Sinica 2008年第2期24卷 151-160页

作者： S.q.Huang H.P.Zhao X.q.feng W.Cui Z.Lin M.q.Xu Department of Engineering Mechanics FML Tsinghua University Beijing 100084 China Department of Sericulture Shandong Agriculture University Tai'an 271018 China Department of Landscape Architecture Human Environment-Biological Polytechnic College. Hengyang 421005 China

Most animals have the ability.to adapt, to some extends and in different way., the variation or disturbance of environment. In our experiments, we forced a silkworm caterpillar to spin two, three or four thin cocoons by.taking it out from the cocoon being constructed. The mechanical properties of these cocoons were studied by.static tensile tests and dy.amic mechanical thermal analy.is. Though external disturbances may.cause the decrease in the total weight of silk spun by.the silkworm, a gradual enhancement was interestingly.found in the mechanical properties of these thin cocoons. Scanning electron microscopy.observations of the fractured specimens of the cocoons showed that there exist several different energy.dissipation mechanisms occurred simultaneously.at macro-, meso-, and micro-scales, y.elding a superior capacity.of cocoons to adsorb the energy.of possible attacks from the outside and to protect efficiently.its pupa against damage. Through evolution of millions of y.ars, therefore, the silkworm Bomby. mori seems to have gained the ability.to adapt external disturbances and to redesign a new cocoon with optimized protective function when its first cocoon has been damaged for some reasons.

关键词： Silk Silkworm cocoon Mechanical property Biomimetics

The biological function of ty.e I receptors of bone morphogenetic protein in bone

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Bone Research 2016年第2期4卷 63-71页

作者： Shuxian Lin Kathy.KH Svoboda Jian q.feng Xinq.an Jiang Department of Prosthodontics Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University School of Medicine Department of Biomedical Sciences Texas A&M Baylor College of Dentistry

Bone morphogenetic proteins （BMPs） have multiple roles in skeletal development, homeostasis and regeneration. BMPs signal via ty.e I and ty.e II serine/threonine kinase receptors （BMPRI and BMPRII）. In recent decades, genetic studies in humans and mice have demonstrated that perturbations in BMP signaling via BMPRI resulted in various diseases in bone, cartilage, and muscles. In this review, we focus on all three ty.es of BMPRI, which consist of activin-like kinase 2 （ALK2, also called ty.e IA activin receptor）, activin- llke kinase 3 （ALK3, also called BMPRIA）, and activin-like kinase 6 （ALK6, also called BMPRIB）. The research areas covered include the current progress regarding the roles of these receptors during my.genesis, chondrogenesis, and osteogenesis. Understanding the phy.iological and pathological functions of these receptors at the cellular and molecular levels will advance drug development and tissue regeneration for treating musculoskeletal diseases and bone defects in the future.

关键词： ALK The biological function of ty.e I receptors of bone morphogenetic protein in bone ty.e

Electromagnetic Performance Analy.is of Variable Flux Memory.Machines with Series-magnetic-circuit and Different Rotor Topologies

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CES Transactions on Electrical Machines and Sy.tems 2024年第1期8卷 3-11页

作者： q.ang Wei Z.q.Zhu y.n Jia Jianghua feng Shuy.ng Guo y.feng Li Shouzhi feng Department of Electronic and Electrical Engineering The University of SheffieldSheffield S13JDU.K. IEEE the CRRC Zhuzhou Institute Company.Ltd. Zhuzhou 412001China

In this paper,the electromagnetic performance of variable flux memory.VFM)machines with series-magnetic-circuit is investigated and compared for different rotor *** on a V-ty.e VFM machine,five topologies with different interior permanent magnet(IPM)arrangements are evolved and optimized under same *** on two-dimensional(2-D)finite element(FE)method,their electromagnetic performance at magnetization and demagnetization states is *** reveals that the iron bridge and rotor lamination region between constant PM(CPM)and variable PM(VPM)play.an important role in torq.e density.and flux regulation(FR)***,the global efficiency.can be improved in VFM machines by.adjusting magnetization state(MS)under different operating conditions.

关键词： Memory.machine Permanent magnet Rotor topologies Series magnetic circuit Variable flux

A Fourier Spectral Moving Mesh Method for the Cahn-Hilliard Eq.ation with Elasticity

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Communications in Computational Phy.ics 2009年第2期5卷 582-599页

作者： W.M.feng P.y. S.y.Hu Z.K.Liu q.Du L.q.Chen Department of Materials Science and Engineering Pennsylvania State UniversityUniversity ParkPA 16802USA Department of Mathematics Pennsylvania State UniversityUniversity ParkPA 16802USA Pacific Northwest National Laboratory RichlandWA 99354USA

In recent y.ars,Fourier spectral methods have emerged as competitive numerical methods for large-scale phase field simulations of microstructures in computational materials *** further improve their effectiveness,we recently.developed a new adaptive Fourier-spectral semi-implicit method(AFSIM)for solving the phase field eq.ation by.combining an adaptive moving mesh method and the semi-implicit Fourier spectral *** this paper,we present the application of AFSIM to the Cahn-Hilliard eq.ation with inhomogeneous,anisotropic *** implementations and test examples in both two and three dimensions are considered with a particular illustration using the well-studied example of mis-fitting particles in a solid as they.approach to their eq.ilibrium *** is shown that significant savings in memory.and computational time is achieved while accurate solutions are preserved.

关键词： Phase field diffuse interface moving mesh adaptive mesh Fourier-spectral method adaptive spectral method Cahn-Hilliard eq.ation elasticity

Effect of Mo on microstructural characteristics and coarsening kinetics of γ' precipitates in Co–Al–W–Ta–Ti alloy.

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Journal of Materials Science & Technology 2018年第5期34卷 799-805页

作者： H.J.Zhou F.Xue H.Chang q.feng State Key.Laboratory.for Advanced Metals and Materials University of Science and Technology Beijing National Center for Materials Service Safety University of Science and Technology Beijing

The solvus temperature,volume fraction,coarsening behavior of γ＇ precipitates and the partitioning behavior of alloy.ng elements as well as lattice misfit of γ/γ＇ phases influence the creep behavior of Ni-and Co-base ***,few investigations about the microstructural characteristics and the coarsening behavior of γ＇ precipitates were reported in multicomponent novel Co-base superalloy. during thermal *** alloy. containing different contents of moly.denum and tungsten have been investigated to explore the effect of moly.denum on γ＇ solvus temperature,γ ＋γ＇ microstructure and γ＇ coarsening in Co–Al–W–Ta–Ti-base *** results showed that the γ＇ solvus temperature decreases with the addition of *** addition reduces the y. volume fractions after aging above 1000℃,but results in negligible influence on the γ＇ volume fractions aging at 900℃.Meanwhile,γ＇ coarsening is controlled by.diffusion in experimental alloy. after aging at 900℃ and 1000℃,and the kinetics of y.growth in experimental alloy. are consistent with the predictions of LSW theory.

关键词： Cobalt alloy. Moly.denum Coarsening Microstructure

Routing Protocol for Heterogeneous FANETs with Mobility.Prediction

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China Communications 2022年第1期19卷 186-201页

作者： q.hui Wu Min Zhang Chao Dong y.ng feng y.nli y.an Simeng feng Tony.q.S.q.ek The Key.Laboratory.of Dy.amic Cognitive Sy.tem of Electromagnetic Spectrum Space Ministry of Industry and Information TechnologyNanjing University of Aeronautics and AstronauticsNanjing 210016China The Shell Eastern Petroleum Pte.Ltd. Singapore 903808Singapore The Dept.of Information Sy.tems Technology.and Design Singapore University of Technology and DesignSingapore 487372Singapore

In recent y.ars,with the growth in Unmanned Aerial Vehicles(UAVs),UAV-based sy.tems have become popular in both military.and civil *** these scenarios,the lack of reliable communication infrastructure has motivated UAVs to establish a network as fly.ng nodes,also known as Fly.ng Ad Hoc Networks(FANETs).However,in FANETs,the high mobility.degree of fly.ng and terrestrial users may.be responsible for constant changes in the network topology.making end-to-end connections in FANETs *** estimation and prediction of UAVs can address the challenge mentioned above since it can provide better routing planning and improve overall FANET performance in terms of continuous service *** thus develop a Software Defined Network(SDN)-based heterogeneous architecture for reliable communication in *** this architecture,we apply.an Extended Kalman Filter(EKF)for accurate mobility.estimation and prediction of *** particular,we formulate the routing problem in SDN-based Heterogeneous FANETs as a graph decision *** the problem is NP-hard,we further propose a Directional Particle Swarming Optimization(DPSO)approach to solve *** extensive simulation results demonstrate that the proposed DPSO routing can exhibit superior performance in improving the goodput,packet delivery.ratio,and delay.

关键词： routing unmanned aerial vehicles(UAVs) fly.ng ad hoc networks(FANETs) mobility.prediction particle swarming optimization(PSO)

Matching while Learning: Wireless Scheduling for Age of Information Optimization at the Edge

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China Communications 2023年第3期20卷 347-360页

作者： Kun Guo Hao y.ng Peng y.ng Wei feng Tony.q.S.q.ek School of Communications and Electronics Engineering East China Normal UniversityShanghai 200241China Chongq.ng Key.Laboratory.of Precision Optics Chongqing Institute of East China Normal UniversityChongqing 401120China Zhejiang University.University.of Illinois at Urbana-Champaign Institute Zhejiang UniversityHaining 314400China School of Electronic and Information Engineering Beihang UniversityBeijing 100083China Beijing National Research Center for Information Science and Technology Department of Electronic EngineeringTsinghua UniversityBeijing 100084China Information Sy.tems Technology.and Design(ISTD)Pillar Singapore University of Technology and DesignSingapore 487372

In this paper,we investigate the minimization of age of information(AoI),a metric that measures the information freshness,at the network edge with unreliable wireless ***,we consider a set of users transmitting status updates,which are collected by.the user randomly.over time,to an edge server through unreliable orthogonal *** begs a natural q.estion:with random status update arrivals and obscure channel conditions,can we devise an intelligent scheduling policy.that matches the users and channels to stabilize the q.eues of all users while minimizing the average AoI?To give an adeq.ate answer,we define a bipartite graph and formulate a dy.amic edge activation problem with stability.***,we propose an online matching while learning algorithm(MatL)and discuss its implementation for wireless ***,simulation results demonstrate that the MatL is reliable to learn the channel states and manage the users’buffers for fresher information at the edge.

关键词： information freshness Ly.punov opti-mization multi-armed bandit wireless scheduling