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A computational particle fluid-dynamics simulation of hydrodynamics in a three-dimensional full-loop circulating fluidized bed: Effects of particle-size distribution

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Particuology 2020年第2期18卷 134-145页

作者： hang Zhang Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049ShaanxiChina

A computational particle fluid-dynamics model coupled with an energy-minimization multi-scale(EMMS)drag model was applied to investigate the influence of particle-size distribution on the hydrodynamics of a three-dimensional full-loop circulating fluidized *** particle systems,including one monodisperse and two polydisperse cases,were *** numerical model was validated by comparing its results with the experimental axial voidage distribution and solid mass *** EMMS drag model had a high accuracy in the computational particle fluid-dynamics simulation of the three-dimensional full-loop circulating fluidized *** total number of parcels in the system(Np)influenced the axial voidage distribution in the riser,especially at the lower part of the *** numerical simulation results showed that axial segregation by size was predicted in the two polydisperse cases and the segregation size increased with an increase in the number of size *** axial voidage distribution at the lower portion of the riser was significantly influenced by particle-size ***,radial segregation could only be correctly predicted in the upper region of the riser in the polydisperse case of three solid species.

关键词： Circulating fluidized bed Computational particle fluid dynamics Particle-size distribution Energy-minimization multiscale model Three-dimensional full-loop simulation

Approximate Controllability for Degenerate Heat Equation with Bilinear Control

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Journal of Systems Science & Complexity 2021年第2期34卷 537-551页

作者： LI Lingfei GAO hang School of Science Northeast Electric Power UniversityJilin 132012China School of Mathematics and Statistics Northeast Normal UniversityChangchun 130024China

This paper investigates the nonnegative approximate controllability for the one-dimensional degenerate heat equation governed by bilinear *** non-controllability and approximate controllability are studied for the *** the control is restricted to act on a fixed domain,it is not *** the control is allowed to mobile,it is approximately controllable.

关键词： Approximate controllability bilinear control degenerate heat equation

Controllability of the Heat Equation with a Control Acting on a Measurable Set

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Chinese Annals of Mathematics,Series B 2012年第1期33卷 149-160页

作者： hang YU School of Mathematical Sciences Fudan UniversityShanghai 200433China

The paper deals with the controllability of a heat equation. It is well-known that the heat equation yt - △y = uxE in （0, T） × Ω with homogeneous Dirichlet boundary conditions is null controllable for any T 〉 0 and any open nonempty subset E of Ω. In this note, the author studies the case that E is an arbitrary measurable set with positive measure.

关键词： Heat equation Measurable sets Null controllability Observabilityinequality

A modified model for isothermal homogeneous and heterogeneous reactions in the boundary-layer flow of a nanofluid

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Applied Mathematics and Mechanics(English Edition) 2020年第3期41卷 479-490页

作者： Naili XU hang XU State Key Laboratory of Ocean Engineering Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration(CISSE)School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China

The homogeneous and heterogeneous reactions in the boundary-layer of a flat surface are considered. The autocatalysts are assumed to be of regular sizes, while the solution is a dilute nanofluid. The heat release due to the chemical reactions is taken into account. The Buongiorno’s model is used to describe the behaviors of this reaction system. This configuration makes the current model be different from all previous publications. Multiple solutions are given numerically to the rescaled nonlinear system, whose stability is verified. The results show that the strength coefficients of the homogeneous and heterogeneous reactions are key factors to cause the appearance of the multiple solutions in the distribution of the chemical reactions. Nanofluids enhance the diffusion of heat and help maintain the stability of chemical reactions.

关键词： nanofluid homogeneous and heterogeneous reactions Buongiorno’s model multiple solutions stability analysis

热塑性纤维素与PVA混溶性的分子动力学模拟

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原子与分子物理学报 2025年第3期42卷 149-158页

作者：冯彦洪陈帅杰孙航华南理工大学机械与汽车工程学院聚合物新型成型装备国家工程研究中心聚合物成型加工工程教育部重点实验室广东省高分子先进制造技术及装备重点实验室广州510000

首次提出了将氧化还原改性纤维素(Oxidation-reduction modified cellulose,ORC)与聚乙烯醇(Poly(vinyl alcohol),PVA)共混进行制备复合材料,并采用分子动力学模拟研究了ORC与PVA的混溶性.对分子链间相互作用能和氢键数量分析发现,随着... 详细信息

首次提出了将氧化还原改性纤维素(Oxidation-reduction modified cellulose,ORC)与聚乙烯醇(Poly(vinyl alcohol),PVA)共混进行制备复合材料,并采用分子动力学模拟研究了ORC与PVA的混溶性.对分子链间相互作用能和氢键数量分析发现,随着改性程度增加,ORC与PVA会产生更强烈的相互作用,这促进了组分间的混溶.当ORC的改性程度达到40%后,ORC与PVA的溶解度参数差值为2.02(J/cm^(3))^(1/2),达到混溶条件.根据Flory-Huggins理论确定了醇解度为88%和99%的PVA与ORC的混溶性,结果表明PVA(88%)与ORC的混溶性更好.对共混体系中形成氢键原子的径向分布函数分析发现,醋酸乙烯酯重复单元上的羰基更倾向与ORC形成分子链间氢键,而乙烯醇重复单元上的羟基更倾向形成分子链内氢键,这促使PVA(88%)/ORC共混体系中形成更多的分子链间氢键,从而混溶性更好.研究结果可为ORC/PVA复合材料的制备提供理论指导.

关键词：混溶性氧化还原改性纤维素分子动力学聚乙烯醇

Evolution of silicon particle damage on fatigue crack initiation and early propagation in an aluminum alloy

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Rare Metals 2023年第7期42卷 2470-2476页

作者： hang Zhou Zheng Zhang School of Materials Science and Engineering Beihang UniversityBeijing100191China

Low-cycle fatigue tests under both mechanical cyclic and thermal cyclic loadings were conducted to study the behavior of fatigue crack initiation and early propagation by means of metallographic and scanning electron microscopy(SEM).The damage mode of silicon particles has significant influence on crack *** are induced from fractured particles in mechanical fatigue or from debonded particles in thermal *** of cracks by breaking through particles happens in particles with non-equiaxial particles,while initiation of cracks from debonded interfaces happens widely in clustered *** cracks induced by fracture particles,the subsequent coalescence of microcracks proceeds through the alternation of brittle fracture of *** sequent broken of particles takes the important part in the early propagation stage of fatigue crack.

关键词： Aluminum alloys Microstructure mechanism Crack initiation Silicon particles

Shape of slab solidification end under non-uniform cooling and its influence on the central segregation with mechanical soft reduction

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International Journal of Minerals,Metallurgy and Materials 2021年第11期28卷 1788-1798页

作者： Jie Li Yan-hui Sun hang-hang An Pei-yuan Ni Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China School of Metallurgy Northeastern UniversityShenyang 110819China Hesteel Group Technology Research Institute Shijiazhuang 050000China

In order to study the effect of continuous casting process parameters on the shape of slab solidification end under non-uniform cooling,a solidification model of a continuous-cast slab with non-uniform cooling condition was established with ProCAST *** model was verified by the results of nail shooting tests and the infrared temperature measurement *** characteristic parameters were defined to evaluate the uniformity of the shape of slab solidification *** results showed that the nonuniformity at the beginning and end of solidification,the solidification end length,and the solidification unevenness increased with the rise of casting *** each 10°C increase of superheat,the solidification unevenness increased by about ***,the effect of superheat on the solidification end length can be *** secondary cooling strength showed minimal effect on the nonuniformity at the beginning and end of *** the increase in secondary cooling intensity,the solidification end length decreased,but the solidification unevenness *** addition,the central segregation of the slab produced with and without the mechanical soft reduction(MSR)process was *** transverse flow of molten steel with low solid fraction influenced the central segregation morphology under MSR.

关键词： continuous casting heat transfer model nail shooting shape of solidification end central segregation

Optimization of strand and final electromagnetic stirrers of round bloom casters with multiple sections

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International Journal of Minerals,Metallurgy and Materials 2016年第10期23卷 1150-1156页

作者： Rui Wang Yan-ping Bao Yi-hong Li hang-hang An State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing School of Material Science and Technology Taiyuan University of Science and Technology

Strand electromagnetic stirring（S-EMS） and final electromagnetic stirring（F-EMS） are the main methods used to improve the center porosity and segregation for round blooms. To optimize the stirring conditions, nail shooting tests were conducted for three sections of large round blooms with diameters of ф380 mm, ф450 mm, and ф600 mm. Acid leaching and sulfur print tests were used to investigate the shell thickness. Based on the results of nail shooting tests, a mathematical model of solidification was established, and the variation of shell thickness and the central solid fraction were exactly calculated by the model. By taking all sections into account, the locations of S-EMS and F-EMS were optimized for each section. In the results, the macro-segregation of various sections is improved after the locations of S-EMS and F-EMS systems are changed.

关键词： continuous casting electromagnetic stirring blooms mathematical models optimization

Null Controllability of Some Degenerate Wave Equations

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Journal of Systems Science & Complexity 2017年第5期30卷 1027-1041页

作者： Zhang Muming GAO hang School of Mathematics and Statistics Northeast Normal UniversityChangchun 130024China.

This paper is devoted to a study of the null controllability problems for one-dimensional linear degenerate wave equations through a boundary controller. First, the well-posedness of linear degenerate wave equations is discussed. Then the null controllability of some degenerate wave equations is established, when a control acts on the non-degenerate boundary. Different from the known controllability results in the case that a control acts on the degenerate boundary, any initial value in state space is controllable in this case. Also, an explicit expression for the controllability time is given. Furthermore, a counterexample on the controllability is given for some other degenerate wave equations.

关键词： Controllability degenerate wave equation Fourier expansion observability.