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Single-source-precursor synthesis of porous W-containing SiC-based nanocomposites as hydrogen evolution reaction electrocatalysts

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Journal of Advanced Ceramics 2021年第6期10卷 1338-1349页

作者： Zhaoju YU Kangwei MAO yao feng College of Materials Key Laboratory of High Performance Ceramic Fibers(Xiamen University)Ministry of EducationXiamen 361005China Technische Universitat Darmstadt Institut fur MaterialwissenschaftOtto-Berndt-Strafie 3D-64287DarmstadtGermany College of Materials Science and Engineering Changsha University of Science&TechnologyChangsha 410114China

In this paper,W-containing SiC-based ceramic nanocomposites were successfully prepared by a polymer-derived ceramic approach using allylhydridopolycarbosilane(AHPCS)as a SiC source,WC16 as a tungsten source,polystyrene(PS)as a pore forming agent as well as divinyl benzene(DVB)as a carbon rich ***-temperature phase behavior of the W-containing SiC-based ceramics after heat treatment was studied,showing that excessive DVB content in the feed will inhibit the crystallinity of W-containing nanoparticles in the final ceramic *** high specific surface area(SSA)of 169.4-276.9 m^(2)/g can be maintained even at high temperature in the range of 1400-1500℃,due to the carbothermal reaction which usually occurs between 1300 and 1400℃.All prepared W-containing SiC-based nanocomposites reveal electrocatalytic activity for the hydrogen evolution reaction(HER).In detail,compared with reversible hydrogen electrode(RHE),the ceramic sample PWA-2-1300 after heat treatment at 1300℃ has the smallest overpotential of 286 mV when the current density is 10 mA·cm^(-2) in acid medium,indicating the promising perspective in the water splitting field.

关键词： single-source-precursor W-containing phase SiC-based nanocomposites electrocatalyst hydrogen evolution reaction

Line profile studies of hydrodynamical models of cometary compact H II regions

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Research in Astronomy and Astrophysics 2015年第6期15卷 828-848页

作者： feng-yao Zhu Qing-feng Zhu Department of Astronomy University of Science and Technology of China Key Laboratory for Research in Galaxies and Cosmology University of Science and Technology of China Chinese Academy of Sciences

We simulate the evolution of cometary H II regions based on several champagne flow models and bow shock models, and calculate the profiles of the [Ne II] fine-structure line at 12.81 μm, the H30α recombination line and the [Ne III] finestructure line at 15.55 μm for these models at different inclinations of 0°, 30° and 60°. We find that the profiles in the bow shock models are generally different from those in the champagne flow models, but the profiles in the bow shock models with lower stellar velocity （≤ 5 km s^-1） are similar to those in the champagne flow models. In champagne flow models, both the velocity of peak flux and the flux weighted central velocities of all three lines point outward from molecular clouds. In bow shock models, the directions of these velocities depend on the speed of stars. The central velocities of these lines are consistent with the stellar motion in the high stellar speed cases, but they are opposite directions from the stellar motion in the low speed cases. We notice that the line profiles from the slit along the symmetrical axis of the projected 2D image of these models are useful for distinguishing bow shock models from champagne flow models. It is also confirmed by the calculation that the flux weighted central velocity and the line luminosity of the [Ne III] line can be estimated from the [Ne II] line and the H30α line.

关键词： H II regions -- ISM kinematics and dynamics clusters -- line profiles

Commuting variety of Witt algebra

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Frontiers of Mathematics in China 2018年第5期13卷 1179-1187页

作者： Yu-feng yao Hao CHANG Department of Mathematics Shanghai Maritime University Shanghai 201306 China School of Mathematics and Statistics Central China Normal University Wuhan 430079 China

Let g = W1 be the Witt algebra over an algebraically closed field k of characteristic p 〉 3, and let ∮（g） = {（x,y） ∈ g×g [x,y] = 0} be the commuting variety of g. In contrast with the case of classical Lie algebras of P. Levy [J. Algebra, 2002, 250： 473-484], we show that the variety ∮（g） is reducible, and not equidimensional. Irreducible components of ∮（g） and their dimensions are precisely given. As a consequence, the variety ∮（g） is not normal.

关键词： Witt algebra irreducible component dimension commuting variety

Borel Subalgebras of the Witt Algebra

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Acta Mathematica Sinica,English Series 2015年第8期31卷 1348-1358页

作者： Yu feng yao Hao CHANG Department of Mathematics Shanghai Maritime University Department of Mathematics East China Normal University

Let F be an algebraically closed field of characteristic p 〉 3, and g be the Witt algebra over F. Let N be the nilpotent cone of g. An explicit description of N is given, so that the conjugacy classes of Borel subalgebras of g under the automorphism group of g are determined. In contrast with only one conjugacy class of Borel subalgebras in a classical simple Lie algebra, there are two conjugacy classes of Borel subalgebras in g. The representatives of conjugacy classes of Borel subalgebras, i.e.,the so-called standard Borel subalgebras, are precisely given.

关键词： Witt algebra Borel subalgebra nilpotent element nilpotent cone automorphism group

Adaptive Backstepping Terminal Sliding Mode Control Method Based on Recurrent Neural Networks for Autonomous Underwater Vehicle

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Chinese Journal of Mechanical Engineering 2018年第6期31卷 228-243页

作者： Chao Yang feng yao Ming-Jun Zhang College of Mechanical and Electrical Engineering Harbin Engineering University Harbin 150001 China

The trajectory tracking control problem is addressed for autonomous underwater vehicle(AUV) in marine environ?ment, with presence of the influence of the uncertain factors including ocean current disturbance, dynamic modeling uncertainty, and thrust model errors. To improve the trajectory tracking accuracy of AUV, an adaptive backstepping terminal sliding mode control based on recurrent neural networks(RNN) is proposed. Firstly, considering the inaccu?rate of thrust model of thruster, a Taylor’s polynomial is used to obtain the thrust model errors. And then, the dynamic modeling uncertainty and thrust model errors are combined into the system model uncertainty(SMU) of AUV; through the RNN, the SMU and ocean current disturbance are classified, approximated online. Finally, the weights of RNN and other control parameters are adjusted online based on the backstepping terminal sliding mode controller. In addition, a chattering?reduction method is proposed based on sigmoid function. In chattering?reduction method, the sigmoid function is used to realize the continuity of the sliding mode switching function, and the sliding mode switching gain is adjusted online based on the exponential form of the sliding mode function. Based on the Lyapu?nov theory and Barbalat’s lemma, it is theoretically proved that the AUV trajectory tracking error can quickly converge to zero in the finite time. This research proposes a trajectory tracking control method of AUV, which can e ectively achieve high?precision trajectory tracking control of AUV under the influence of the uncertain factors. The feasibility and e ectiveness of the proposed method is demonstrated with trajectory tracking simulations and pool?experi?ments of AUV.

关键词： Autonomous underwater vehicle(AUV) Trajectory tracking Neural networks Backstepping method Terminal sliding mode Adaptive control

Effect of content and spin state of iron on electronic properties and floatability of iron-bearing sphalerite:A DFT+U study

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International Journal of Mining Science and Technology 2023年第12期33卷 1563-1571页

作者： yao feng Zhuofan Li Jianhua Chen Ye Chen State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures School of Chemistry&Chemical EngineeringGuangxi UniversityNanning 530004China MOE Key Laboratory of New Processing Technology for Nonferrous Metals and Materials Guangxi UniversityNanning 530004China School of Resources Environment and MaterialsGuangxi Higher School Key Laboratory of Minerals EngineeringGuangxi UniversityNanning 530004China

Iron is an impurity widely occurred in sphalerite,and its effect on sphalerite flotation is *** this work,the effects of iron content and spin state on electronic properties and floatability of iron-bearing sphalerite are comprehensively studied using density functional theory Hubbard U(DFT+U)calculations combined with coordination chemistry *** band gap of ideal sphalerite is 3.723 eV,and thus electron transition is difficult to occur,resulting in poor *** results suggest the band gap of sphalerite decreases with increasing iron *** low iron content,the decreased band gap facilitates electron transition;at this case,Fe^(2+)in a high-spin state possesses oneπelectron pair,which can form a weakπ-backbonding with xanthate,causing increasing ***,for medium and high iron-bearing sphalerite,with the further decrease of band gap,Fe^(2+)is oxidized to Fe^(3+)due to electrochemical interaction,and henceπ-backbonding is eliminated,leading to lower floatability of iron-bearing sphalerite,which is consistent with the flotation experimental *** work could give a deeper understanding of how sphalerite flotation behaviors are affected by iron content.

关键词： Sphalerite Iron-bearing sphalerite Iron content Spin state Density functional theory

Observation scheduling problem for AEOS with a comprehensive task clustering

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Journal of Systems Engineering and Electronics 2021年第2期32卷 347-364页

作者： CHANG Zhongxiang ZHOU Zhongbao yao feng LIU Xiaolu School of Business Administration Hunan UniversityChangsha 410082China Institute of Data Science and Decision Optimization Hunan UniversityChangsha 410082China Department of Mathematics Simon Fraser UniversitySurrey V3T 0A3Canada School of System Engineering National University of Defense TechnologyChangsha 410073China

Considering the flexible attitude maneuver and the narrow field of view of agile Earth observation satellite(AEOS)together,a comprehensive task clustering(CTC)is proposed to improve the observation scheduling problem for AEOS(OSPFAS).Since the observation scheduling problem for AEOS with comprehensive task clustering(OSWCTC)is a dynamic combination optimization problem,two optimization objectives,the loss rate(LR)of the image quality and the energy consumption(EC),are proposed to format OSWCTC as a bi-objective optimization *** the power of an adaptive large neighborhood search(ALNS)algorithm with a nondominated sorting genetic algorithm II(NSGA-II),a bi-objective optimization algorithm,ALNS+NSGA-II,is developed to solve *** on the existing instances,the efficiency of ALNS+NSGA-II is analyzed from several aspects,meanwhile,results of extensive computational experiments are presented which disclose that OSPFAS considering CTC produces superior outcomes.

关键词： observation scheduling comprehensive task clustering(CTC) bi-objective optimization image quality energy consumption(EC)

Droplets breakup via a splitting microchannel

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Chinese Physics B 2020年第5期29卷 377-386页

作者： Wei Gao Cheng Yu feng yao School of Engineering and Applied Sciences Harvard UniversityCambridgeMA 02138USA Department of Mechanical Engineering University of Hawaii at ManoaHonoluluHI 96822USA Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application School of Environmental Science and EngineeringSuzhou University of Science and TechnologySuzhou 215009China

On the basis of a volume of fluid(VOF)liquid/liquid interface tracking method,we apply a two-dimensional model to investigate the dynamic behaviors of droplet breakup through a splitting *** feasibility and applicability of the theoretical model are experimentally *** flow regimes are observed in the splitting microchannel,that is,breakup with permanent obstruction,breakup with temporary obstruction,breakup with tunnels,and *** results indicate that the increase of the capillary number Ca provides considerable upstream pressure to accelerate the droplet deformation,which is favorable for the droplet *** decrease of the droplet size contributes to its shape changing from the plug to the sphere,which results in weakening droplet deformation ability and generating the nonbreakup flow regime.

关键词： microfluidics droplet splitting hydrodynamic numerical simulation

L^q Interior Estimates of the Gradient for Weak Solutions of Quasilinear Elliptic Equations

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Acta Mathematica Sinica,English Series 2007年第12期23卷 2225-2234页

作者： feng Ping yao Yong Yong CAI LMAM School of Mathematical Sciences Peking University Bering 100871 P. R. China

The authors present a new proof of L^q interior estimates of the gradient for weak solutions of a quasilinear elliptic equation of p-Laplacian type.

关键词： L^q interior estimates weak solutions quasilinear elliptic maximal function