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Numerical simulation of local and global mixing/segregation characteristics in a gas–solid fluidized bed

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Chinese Journal of Chemical Engineering 2022年第4期35卷 72-86页

作者： Zhen wan Youjun lu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

Researches on solids mixing and segregation are of great significance for the operation and design of fluidized bed *** this paper,the local and global mixing and segregation characteristics of binary mixtures were investigated in a gas–solid fluidized bed by computational fluid dynamics-discrete element method(CFD-DEM)coupled approach.A methodology based on solids mixing entropy was developed to quantitatively calculate the mixing degree and time of the *** mixing curves of global mixing entropy were acquired,and the distribution maps of local mixing entropy and mixing time were also *** comparing different operating conditions,the effects of superficial gas velocity,particle density ratio and size ratio on mixing/segregation behavior were *** showed that for the partial mixing state,the fluidized bed can be divided into three parts along the bed height:complete segregation area,transition area and stable mixing *** areas showed different mixing/segregation *** gas velocity promoted the local and global mixing of binary *** increase in particle density ratio and size ratio enlarged the complete segregation area,reduced the mixing degree and increased the mixing time in the stable mixing area.

关键词： Discrete element method Solids mixing Binary mixtures Fluidized bed

Highly parallel implementation of sub-pixel interpolation for AVS HDTV decoder

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第12期9卷 1638-1643页

作者： wan-yi LI lu YU Institute of Information and Communication Engineering Zhejiang University Hangzhou 310027 China

In this paper, we propose an effective VLS1 architecture of sub-pixel interpolation for motion compensation in the AVS HDTV decoder. To utilize the similar arithmetical operations of 15 luma sub-pixel positions, three types of interpolation filters are proposed. A simplified multiplier is presented due to the limited range of input in the chroma interpolation process. To improve the processing throughput, a parallel and pipelined computing architecture is adopted. The simulation results show that the proposed hardware implementation can satisfy the real-time constraint for the AVS HDTV （1 920× 1 088） 30 fps decoder by operating at 108 MHz with 38.18k logic gates. Meanwhile, it costs only 216 cycles to accomplish one macroblock, which means the B frame sub-pixel interpolation can be realized by using only one set of the proposed architecture under real-time constraints.

关键词： VLSI architecture Interpolation AVS HDTV

Preparation of Multifunctional β-hemihydrate Gypsum using Oyster Shell Powder as the Partial Replacement of Ag/TiO2 Particle

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Journal of Wuhan University of Technology(Materials Science) 2020年第6期35卷 1073-1080页

作者： wan lu China Shanghai Architectural Design&Reserach Institute Co.Ltd. Shanghai 20062China

This work aimed to use oyster shell powder (OSP) as the partial replacement of Ag/TiO2 particle to obtain multifunctional β-hemihydrate ***,the β-hemihydrate gypsum was mixed with different contents of OSP and Ag/TiO2 *** and MB removal experiments were conducted to assess the antibacterial characteristic and photocatalytic activity of β-hemihydrate gypsum with Ag/TiO2 particle and ***,the formaldehyde degradation test was carried out to evaluate its formaldehyde removal ***,their setting times,compressive and flexural strengths at 1,3,and 28 days were comparatively *** experimental results prove that the composite use of OSP and Ag/TiO2 particle provide feasible multifunction for the β-hemihydrate *** can further improve the bactericidal rates and exhibit extra MB removal ratios compared with the gypsum plasters with single Ag/TiO2 ***,they can increase the formaldehyde degradation ratios,and this promotion is related to the introduction of Ag/TiO2 ***,OSP delays the initial setting time but promotes the final setting time of β-hemihydrate gypsum,and Ag/TiO2 particle hardly affects the setting ***,OSP reduces the strengths of plasters at 1,3,and 28 *** in general,the composite addition of OSP and Ag/TiO2 particle increase the compressive and flexural strengths of gypsum plasters at 1,3,and 28 *** results provide theoretical guidance for the recycling of OSP and the preparation of gypsum-based products with antibacterial and formaldehyde degradation capabilities.

关键词： oyster shell powder Ag/TiO2 particle β-hemihydrate gypsum bactericidal rate setting times

Particle convective heat transfer near the wall in a supercritical water fluidized bed by single particle model coupled with CFD-DEM

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Particuology 2023年第2期73卷 47-58页

作者： Tianning Zhang Zhen wan Youjun lu State Key Laboratory of Multiphase Flow in Power Engineering(SKLMFPE) Xi'an Jiaotong UniversityXi'an710049ShaanxiChina Xi'an Electronic Engineering Research Institute Xi'an710100ShaanxiChina

Supercritical water fluidized bed(SCWFB)is a promising reactor to gasify biomass or *** optimization design is closely related to wall-to-bed heat transfer,where particle convective heat transfer plays an important *** paper evaluates the particle convective heat transfer coefficient(h_(pc))at the wall in SCWFB using the single particle *** critical parameters in the single particle model which is difficult to get experimentally are obtained by the computational fluid dynamics-discrete element method(CFD-DEM).The contact statistics related to particle-to-wall heat transfer,such as contact number and contact distance,are also *** results show that particle residence time(τ),as the key parameter to evaluate h_(pc),is found to decrease with rising velocity,while increase with larger thermal boundary layer thickness.τfollows a gamma function initially adopted in the gas-solid fluidized bed,making it possible to evaluate h_(pc) in SCWFB by a simplified single particle *** theoretical predicted h_(pc) tends to increase with rising thermal gradient thickness at a lower velocity(1.5 U_(mf)),while first decreases and then increases at higher velocity(1.75 and 2 U_(mf)).h_(pc) occupies 30%-57%of the overall wall-to-bed heat transfer coefficient for a particle diameter of 0.25 *** results are helpful to predict the overall wall-to-bed heat transfer coefficient in SCWFB combined with a reasonable fluid convective heat transfer model from a theoretical perspective.

关键词： Supercritical water Fluidized bed Particle residence time Discrete element method Single particle model

Instantaneous mixing characteristics of binary mixtures differing in density in a gas-solid fluidised bed

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Particuology 2020年第6期18卷 63-71页

作者： Zhen wan Youjun lu Hao wang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049ShaanxiChina

Characterisations of instantaneous mixing behaviours in fluidised beds with binary mixtures has many *** studied the instantaneous mixing characteristics of binary mixtures in a 2-D quasi gas-solid fluidised bed using a capacitance probe *** method enabled the quantitative assessment of instantaneous mixing behaviours,including mixing index,rate,and *** kinds of binary mixtures of similar size but different density were used for the transient and steady fluidisation experiments in a bubbling fluidised *** mixing curves of initially segregated binary mixtures were acquired,and the instantaneous characteristics for the entire process were *** equation was proposed to describe the mixing process and predict the mixing degree over *** comparing experiments with different working conditions,the effects of superficial gas velocity and density ratio on the mixing in the centre and at the wall of the fluidised bed were *** the stable fluidisation stage,the axial concentration profiles of the mixtures were obtained,and the mechanisms of mixing were *** showed that the mixing level increased logarithmically with time and eventually reached a relatively stable *** the superficial gas velocity and reducing the density ratio promoted mixing and reduced mixing *** superficial gas velocities tended to mix the mixtures well and quickly,regardless of the density ratio of the two components.

关键词： Binary mixtures Fluidised bed Mixing Instantaneous characteristics

NUMERICAL ANALYSIS FOR A MEAN-FIELD EQUATION FOR THE ISING MODEL WITH GLAUBER DYNAMICS

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Journal of Computational Mathematics 1997年第3期15卷 203-218页

作者： lu, BN wan, GH SHAANXI NORMAL UNIV DEPT MATHXIANPEOPLES R CHINA

In this paper, a mean-field equation of motion which is derived by Penrose (1991) for the dynamic Ising model with Glauber dynamics is considered. Various finite difference schemes such as explicit Euler scheme, predictor-corrector scheme and some implicit schemes are given and their convergence, stabilities and dynamical properties are discussed. Moreover, a Lyapunov functional for the discrete semigroup {S}(n>0) is constructed. Finally, numerical examples are computed and analyzed. it shows that the model is a better approximation to Cahn-Allen equation which is mentioned in Penrose (1991).

关键词： Figure NUMERICAL ANALYSIS FOR A MEAN-FIELD EQUATION FOR THE ISING MODEL WITH GLAUBER DYNAMICS Math

Growth of Casting Microcrack and Micropore in Single-crystal Superalloys Analysed by Three-Dimensional Unit Cell

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Journal of Materials Science & Technology 2006年第2期22卷 183-189页

作者： Jiansong wan Zhenzhou lu Zhufeng YUE Department of Engineering Mechanics Northwestern Polytechnical University Xi＇an 710072 China

Finite element （FE） analysis was employed to investigate the casting microcrack and micropore growth in nickel-base single-crystal superalloys DD3. Based on the finite deformation rate-dependent crystallographic constitutive equation, the simulations of casting microcrack and micropore growth in three-dimensional unit cell model were carried out in a range of parameters including stress triaxiality, Lode parameter and type of activated slip systems. The FE results show that the stress triaxiality has profound effects on growth behavior, and the Lode parameter is also important for the casting microcrack and micropore growth. The type of operative slip systems has remarkable effect on casting microcrack and micropore growth, so the life of single- crystal component is associated with the type of activated slip systems, which is related to Schmid factor and the number of activated slip systems. The growth comparison between microcrack and micropore reveals that when the material is subjected to large deformation, the growth rate of microcrack is faster than that of micropore, i.e. microcrack is more dangerous than micropore; the microcrack is easier to result in brittle fracture than micropore. The stress triaxiality and Lode parameter have strong influence on the growth of microcrack and micropore.

关键词： Casting micropore Casting crack Single-crystal superalloys Crystallographic constitutive equation

THE GLOBAL DUFORT-FRANKEL DIFFERENCE APPROXIMATION FOR NONLINEAR REACTION-DIFFUSION EQUATIONS

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Journal of Computational Mathematics 1998年第3期16卷 275-288页

作者： lu, BN wan, GH Guo, BL Xiangtan Univ Inst Computat & Appl Math Xiangtan 411105 Peoples R China Inst Appl Phys & Computat Math Lab Computat Phys Beijing 100088 Peoples R China Shaanzi Normal Univ Dept Math Xian 710062 Peoples R China Inst Appl Phys & Computat Math Ctr Nonlinear Studies Beijing 100088 Peoples R China

In this paper, the initial value problem of nonlinear reaction-diffusion equation is considered. The Dufort-Frankel finite difference approximation for the long time scheme is given for the d-dimensional reaction-diffusion equation with the two different cases. The global solution and global attractor are discussed for the Dufort-Frankel scheme. Moreover properties of the solution are studied. The error estimate is presented in a finite time region and in the global time region for some special cases. Finally the numerical results for the equation are investigated for Allen-Cahn equation and some other equations and the homoclinic orbit is simulated numerically.

关键词： global Dufort-Frankel method reaction-diffusion equation global attractor error estimate numerical experiments

CBA: multi source fusion model for fast and intelligent target intention identification

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Journal of Systems Engineering and Electronics 2024年第2期35卷 406-416页

作者： wan Shichang LI Qingshan wanG Xuhua lu Nanhua School of Computer Science and Technology Xidian UniversityXi’an 710071China School of Mathematics and Computer Application Shangluo UniversityShangluo 726000China

How to mine valuable information from massive multisource heterogeneous data and identify the intention of aerial targets is a major research focus at present. Aiming at the longterm dependence of air target intention recognition, this paper deeply explores the potential attribute features from the spatiotemporal sequence data of the target. First, we build an intelligent dynamic intention recognition framework, including a series of specific processes such as data source, data preprocessing,target space-time, convolutional neural networks-bidirectional gated recurrent unit-atteneion (CBA) model and intention recognition. Then, we analyze and reason the designed CBA model in detail. Finally, through comparison and analysis with other recognition model experiments, our proposed method can effectively improve the accuracy of air target intention recognition,and is of significance to the commanders’ operational command and situation prediction.

关键词： intention massive data deep network artificial intelligence