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A Multi-phase Field Model for Static Recrystallization of Hot Deformed Austenite in a C–Mn Steel

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Acta Metallurgica Sinica(English Letters) 2018年第2期31卷 208-215页

作者： Jun Zhang Cheng-wu Zheng Dian-Zhong Li School of Chemistry and Materials Science University of Science and Technology of China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences

A multi-phase-field model has been developed to simulate the microstructure evolution and kinetics of the austenite static recrystallization（SRX） in a C–Mn steel. In this model, the bulk free energy that coupling the deformation stored energy with a special interpolation function is incorporated. Both the deformed grain topology and the deformation stored energy have been included in order to investigate the influence of pre-deformation on the subsequent austenite SRX at different hot deformation levels. Diverse scenarios of microstructure evolution show different deformation-dependent recrystallized grain sizes. The transformation kinetics is then discussed by analyzing the overall SRX fraction and the average interface velocity on the recrystallization front.

关键词： Phase-field Static recrystallization Microstructure evolution Hot deformation Mesoscopic modeling

Aerobic N_2O emission for activated sludge acclimated under different aeration rates in the multiple anoxic and aerobic process

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Journal of Environmental Sciences 2016年第5期28卷 70-79页

作者： Huoqing Wang Yuntao Guan Min Pan Guangxue wu key Laboratory of Microorganism Application and Risk Control of Shenzhen Graduate School at Shenzhen Tsinghua University Environmental Science and Technology Xiamen University of Technology

Nitrous oxide（N_2O） is a potent greenhouse gas that can be emitted during biological nitrogen removal. N_2O emission was examined in a multiple anoxic and aerobic process at the aeration rates of 600 m L/min sequencing batch reactor（SBRL） and 1200 m L/min（SBRH）.The nitrogen removal percentage was 89% in SBRLand 71% in SBRH, respectively. N_2O emission mainly occurred during the aerobic phase, and the N_2O emission factor was 10.1%in SBRLand 2.3% in SBRH, respectively. In all batch experiments, the N_2O emission potential was high in SBRLcompared with SBRH. In SBRL, with increasing aeration rates, the N_2O emission factor decreased during nitrification, while it increased during denitrification and simultaneous nitrification and denitrification（SND）. By contrast, in SBRHthe N_2O emission factor during nitrification, denitrification and SND was relatively low and changed little with increasing aeration rates. The microbial competition affected the N_2O emission during biological nitrogen removal.

关键词： Aeration rate Nitrous oxide Biological nitrogen removal Multiple anoxic and aerobic Nitrite accumulation

An adaptive fuzzy filter for coding artifacts removal in video and image

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第6期8卷 841-848页

作者： wu Jing YE Xiu-qing GU Wei-kang Department of Information and Communication Engineering Zhejiang University Hangzhou 310027 China

This paper proposes a new adaptive post-filtering algorithm to remove coding artifacts in block-based video coder. The proposed method concentrates on blocking and ringing artifacts removal. For de-blocking, the blocking strength is identified to determine the filtering range, and the maximum quantization parameter of the image is used to adapt the 1D fuzzy filter. For de-ringing, besides the edge detection, a complementary ringing detection method is proposed to locate the neglected ringing blocks, and the gradient threshold is adopted to adjust the parameter of 2D fuzzy filter. Experiments are performed on the MPEG-4 sequences. Compared with other methods, the proposed one achieves better detail preservation and artifacts removal performance with lower computational cost.

关键词： Adaptive fuzzy filter Blocking artifacts Ringing artifacts De-blocking De-ringing

Effects of Machine Tool Configuration on Its Dynamics Based on Orthogonal Experiment Method

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Chinese Journal of Aeronautics 2012年第2期25卷 285-291页

作者： GAO Xiangsheng ZHANG Yidu ZHANG Hongwei wu Qiong State key Laboratory of Virtual Reality Technology and Systems Beihang University Beijing 100191 China School of Mechanical Engineering Beijing Institute of Petrochemical Technology Beijing 102617 China

In order to analyze the influence of configuration parameters on dynamic characteristics of machine tools in the working space, the configuration parameters have been suggested based on the orthogonal experiment method. Dynamic analysis of a milling machine, which is newly designed for producing turbine blades, has been conducted by utilizing the modal synthesis method. The finite element model is verified and updated by experimental modal analysis （EMA） of the machine tool. The result gained by modal synthesis method is compared with whole-model finite element method （FEM） result as well. According to the orthogonal experiment method, four configuration parameters of machine tool are considered as four factors for dynamic characteristics. The influence of configuration parameters on the first three natural frequencies is obtained by range analysis. It is pointed out that configuration parameter is the most important factor affecting the fundamental frequency of machine tools, and configuration parameter has less effect on lower-order modes of the system than others. The combination of configuration parameters which makes the fundamental frequency reach the maximum value is provided. Through demonstration, the conclusion can be drawn that the influence of configuration parameters on the natural frequencies of machine tools can be analyzed explicitly by the orthogonal experiment method, which offers a new method for estimating the dynamic characteristics of machine tools.

关键词： configuration parameter dynamic characteristics modal synthesis method substructure orthogonal experiment method

Multi-population and diffusion UMDA for dynamic multimodal problems

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Journal of Systems Engineering and Electronics 2010年第5期21卷 777-783页

作者： Yan wu Yuping Wang Xiaoxiong Liu Jimin Ye School of Sciences Xidian University Xi'an 710071 R R. China School of Computer Science and Technology Xidian University Xi'an 710071 P. R. China College of Automation Northwestern Polytechnical University Xi'an 710072 P. R. China

In dynamic environments,it is important to track changing optimal solutions over *** marginal distribution algorithm（UMDA） which is a class algorithm of estimation of distribution algorithms attracts more and more attention in recent *** this paper a new multi-population and diffusion UMDA（MDUMDA） is proposed for dynamic multimodal *** multi-population approach is used to locate multiple local optima which are useful to find the global optimal solution quickly to dynamic multimodal *** diffusion model is used to increase the diversity in a guided fashion,which makes the neighbor individuals of previous optimal solutions move gradually from the previous optimal solutions and enlarge the search *** approach uses both the information of current population and the part history information of the optimal *** experimental studies on the moving peaks benchmark are carried out to evaluate the proposed algorithm and compare the performance of MDUMDA and multi-population quantum swarm optimization（MQSO） from the *** experimental results show that the MDUMDA is effective for the function with moving optimum and can adapt to the dynamic environments rapidly.

关键词： univariate marginal distribution algorithm(UMDA) dynamic multimodal problems dynamic optimization multipopulation scheme.

Geomagnetic Shielding Property and Mechanism of Fe–Ni Laminated Composite

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Acta Metallurgica Sinica(English Letters) 2014年第5期27卷 918-923页

作者： Xiangyu Ma Qiang Zhang Xiang Chen Gaohui wu School of Material Science and Engineering Harbin Institute of Technology Department of Applied Science and Technology Politecnico di Torino

Ni layers were deposited on the two sides of pure Fe substrate by using electroplating to form Ni/Fe/Ni diffusion couple. After diffusion heat treatment, Fe-Ni laminated composite was obtained with Fe-Ni alloy/Fe/Fe-Ni alloy structure. The results indicate that the Fe-Ni layers combine well with the substrate and the Fe-Ni/Fe interface presents an interlocking microstructure with small-size grains. The concentration of element Ni in the Fe-Ni layer decreases from surface to interior exhibiting a gradient distribution. Geomagnetic shielding factor （SF） of Fe-Ni laminated composite can reach as high as 22.6, which is about seven times of that of pure Fe substrate. Mathematical equation of SF for laminated structure was derived according to magnetic circuit and resistance theory. The theoretical expression reveals that parameters such as the thickness and magnetic permeability of the shield material play an important role in the magnetic shielding behavior and the theoretical calculation results of SF coincide well with our experimental values.

关键词： Fe-Ni laminated composite Initial permeability Magnetic shield Shielding factor

On the Mathematical Nature of Wireless Broadcast Trees

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Tsinghua Science and Technology 2018年第3期23卷 223-232页

作者： Fulu Li Junwei Cao Chunfeng Wang kui wu Research Instituteof Information Technology Tsinghua University Beijing100084 China Qian Xuesen Laboratory of Space Technology China Academy of Space TechnologyBeijing 100094 China. Department of Computer Science University of Victoria BC VBW3P6 Canada.

Trees are arguably one of the most important data structures widely used in information theory and computing science. Different numbers of intermediate nodes in wireless broadcast trees may exert great impacts on the energy consumption of individual nodes, which are typically equipped with a limited power supply in a wireless sensor network; this limitation may eventually determine how long the given wireless sensor network can last. Thus, obtaining a deep understanding of the mathematical nature of wireless broadcast trees is of great importance. In this paper, we give new proof of Cayley＇s well-known theorem for counting labeled trees. A distinct feature of this proof is that we purely use combinatorial structures instead of constructing a bijection between two kinds of labeled trees, which is in contrast to all existing proofs. Another contribution of this work is the presentation of a new theorem on trees based on the number of intermediate nodes in the tree. To the best of our knowledge,this work is the first to present a tree enumeration theorem based on the number of intermediate nodes in the tree.

关键词： energy efficiency tree theorem broadcast trees wireless transmissions

Modeling and simulation of chemically reacting flows in gas-solid catalytic and non-catalytic processes

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Particuology 2010年第6期8卷 525-530页

作者： Changning wu Binhang Yan Yong Jin Yi Cheng Department of Chemical Engineering Tsinghua University Beijing 100084 China

This paper gives an overview of the recent development of modeling and simulation of chemically react- ing flows in gas-solid catalytic and non-catalytic processes. General methodology has been focused on the Eulerian-Lagrangian description of particulate flows, where the particles behave as the catalysts or the reactant materials. For the strong interaction between the transport phenomena （i.e., momentum, heat and mass transfer） and the chemical reactions at the particle scale, a cross-scale modeling approach, i.e., CFD-DEM or CFD-DPM, is established for describing a wide variety of complex reacting flows in multiphase reactors, Representative processes, including fluid catalytic cracking （FCC）, catalytic conversion of syngas to methane, and coal pyrolysis to acetylene in thermal plasma, are chosen as case studies to demonstrate the unique advantages of the theoretical scheme based on the integrated particle-scale information with clear physical meanings, This type of modeling approach provides a solid basis for understanding the multiphase reacting flow problems in general.

关键词： Gas-solid chemically reacting flow Cross-scale modeling and simulation Eulerian-Lagrangian scheme Computational fluid dynamics (CFD) Discrete element method (DEM) Discrete phase model (DPM)

GENERATING EXACT NONLINEAR RANkING FUNCTIONS BY SYMBOLIC-NUMERIC HYBRID METHOD

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Journal of Systems Science & Complexity 2013年第2期26卷 291-301页

作者： SHEN Liyong wu Min YANG Zhengfeng ZENG Zhenbing School of Mathematical Sciences Graduate University of Chinese Academy of Sciences Shanghai key Laboratory of Trustworthy Computing East China Normal University

This paper presents a hybrid symbolic-numeric algorithm to compute ranking functions for establishing the termination of loop programs with polynomial guards and polynomial *** authors first transform the problem into a parameterized polynomial optimization problem,and obtain a numerical ranking function using polynomial sum-of-squares relaxation via semidefinite programming(SDP).A rational vector recovery algorithm is deployed to recover a rational polynomial from the numerical ranking function,and some symbolic computation techniques are used to certify that this polynomial is an exact ranking function of the loop *** last,the authors demonstrate on some polynomial loop programs from the literature that our algorithm successfully yields nonlinear ranking functions with rational coefficients.

关键词： Program verification ranking function semidefinite programming symbolic-numeric hybrid method.