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Characterization of thermal-induced distorted face-centered cubic structure in pure titanium

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Journal of Iron and Steel Research International 2019年第6期26卷 653-658页

作者： Hai-chen Wu Xiao-fang Bi school of Materials science and engineering Beihang University Beijing 100191 China

After 900 ℃ high-vacuum annealing and air cooling, a special band was observed in pure titanium. Energy-dispersive spectrum showed that the composition of the band and the matrix is the same. By tilting the band to different zone axes and taking selected-area electron diffraction (SAED) patterns, we found that the structure of the band is distorted face-centered cubic (fcc) with the lattice constants a, b, and c deviating slightly from each other on the basis of the analyses of the SAED patterns together with the tilting angles. The lattice constants a, b, and c are calculated based on the measurement of interplanar spacing according to high-resolution transmission electron microscopy (HRTEM) images. The orientation relation between the hexagonal-close-packed (hcp) matrix and the distorted fcc band is [11(2)0]hcp//[110]fcc and (0001)hcp//(1(1)1)fcc according to SAED analysis. The phase boundary between the matrix and the band was observed to demonstrate serrated configuration composed of two kinds of micro-steps: ((1)11)//(0002) and ((1)11)//(10(1)1) on the basis of Cs-corrected HRTEM characterization. The distorted fcc band is deduced to be a thermal-induced metastable phase transformed from the high-temperature body-centered cubic (bcc) structure during the allotropic transformation from bcc to hcp based on orientation relation analysis.

关键词： Titanium Transmission electron microscopy Distorted fee Phase boundary Formation mechanism

BENDING BEHAVIOR OF EMPTY AND FOAM-FILLED ALUMINUM TUBES WITH DIFFERENT CROSS-SECTIONS

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Acta Mechanica Solida Sinica 2012年第6期25卷 616-626页

作者： M. H. Shojaeifard H. R. Zarei R. Talebitooti M. Mehdikhanlo school of Automotive engineering Iran University of Science and Technology Faculty of Aerospace engineering Aeronautical University of Science and Technology

In this paper, the energy absorption mechanism of empty and foam-filled aluminum tubes with different cross-sections （circular, square and elliptic） under bending load is investigated numerically. The load-displacement curves of the present simulations are in very good agreement with those of published experimental data. Here, the existing analytical formulations are reviewed and compared with experimental results. In addition, the effects of different cross-sections and wall thicknesses on the energy absorption capacity and specific energy absorption of these tubes are fully investigated. The results indicate that the energy absorption of an elliptic foam-filled tube with 1.5 mm and 2 mm thicknesses increases about 45% and 73% in comparison with a square one, respectively.

关键词： plastic bending foam filled energy absorption

Effect of heat treatment on microstructure and mechanical properties of Ti-containing low alloy martensitic wear-resistant steel

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China Foundry 2023年第4期20卷 329-338页

作者： Kai Lan Wang Ding Yi-tao Yang school of Materials science and engineering Shanghai UniversityShanghai 200444China

Effects of quenching temperature and cooling conditions(water cooling and 10%NaCl cooling)on microstructure and mechanical properties of a 0.2%Ti low alloy martensitic wear-resistant steel used for die casting ejector plate were *** results show that lath martensite can be obtained after austenitizing in the range of 860-980℃and then water *** an increase in austenitizing temperature,the precipitate content gradually *** precipitates are mainly composed of TiC and Ti4C2S2,and their total content is between 1.15wt.%and 1.64wt.%.The precipitate phase concentration by water-cooling is higher than that by10%NaCl cooling due to the lower cooling rate of water *** the austeniting temperature increases,the hardness and tensile strength of both water cooled and 10%NaCl cooled steels firstly increase and then *** experimental steel exhibits the best comprehensive mechanical properties after being austenitized at 900℃,cooled by 10%NaCl,and then tempered at 200℃.Its hardness,ultimate tensile strength,and wear rate reach551.4 HBW,1,438.2 MPa,and 0.48×10^(-2)mg·m^(-1),respectively.

关键词： low alloy wear-resistant steel quenching temperature cooling condition precipitate retained austenite wear resistance

Microstructure and wear properties of the electroslag remelting layer reinforced by TiC particles

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Journal of University of science and Technology Beijing 2008年第6期15卷 769-774页

作者： Qianlin Wu Yangshan Sun Guoqing Li school of Material science and engineering Southeast University Nanjing 211189 China

The electroslag remelting （ESR） layer reinforced by TiC particles was obtained by electroslag remelting. The microstructure and wear properties of the ESR layer were studied by means of scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and wear test. The results indicate that TiC particles are synthesized by self-propagating high-temperature synthesis （SHS） reaction during the electroslag remelting process. The size of TiC particles is in the range of 1-10 μm, and the distribution of TiC particles is uniform, from outside to inside of the ESR layer, and the volume fraction and the size of TiC particles decrease gradually. Molten iron and slag flow into porosity due to the SHS process leading to rapid densification and the elimination of porosity in the ESR layer during the ESR process. TiC particles enhance the wear resistance of the ESR layer, whereas CaF2 can improve the high temperature lubricating property of the ESR layer.

关键词： electroslag remelting (ESR) TiC particles porosity wear resistance lubricating property

Optimization Based on Convergence Velocity and Reliability for Hydraulic Servo System

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Chinese Journal of Aeronautics 2009年第4期22卷 407-412页

作者： Muhammad Babar Nazir school of Automation science and Electrical engineering Beijing University of Aeronautics and Astronautics

This article presents an optimal hybrid fuzzy proportion integral derivative （HFPID） controller based on combination of proportion integral derivative （PID） and fuzzy controllers, by which the parameters could be evaluated by global optimization either in convergence velocity or in convergence reliability. Focusing on the nonlinear factors of hydraulic servo system, this article takes advantage of PID and fuzzy logic controller integrated with scaling factors to acquire precise tracking performances. To further improve the performances, it provides new developed optimization with rapid convergence to attain reliable approach probability. Focusing on the performance indictors of evolutionary algorithm, this article presents a new technique to predict reliability of the optimization algorithm. Statistics authenticates the effectiveness and robustness of the optimization. Further, many simulation and experimental results indicate that the optimal HFPID could acquire perfect immunity against parametric uncertainties with external disturbance.

关键词： adaptive control system novel evolutionary algorithm hydraulic control equipment convergence velocity convergencereliability optimization

Comparison of different algicides on growth of Microcystis aeruginosa and microcystin release, as well as its removal pathway in riverways

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Frontiers of Environmental science & engineering 2017年第6期11卷 19-26页

作者： Naiyu Wang Kai Wang Can Wang school of Environmental science and engineering Tianjin University Tianjin 300350 China

Eutrophication with a large number of Microcystis aeruginosa commonly occurs worldwide, thereby threatening the aquatic ecosystem and human health. In this study, four kinds of algicides were tested to explore their influence on cell density and chlorophyll-a of M. aeruginosa. Results showed that aluminum silicate agent, which inhibited more than 90% cell growth compared with the control group, demonstrated the strongest inhibition effect immediately on M. aeruginosa growth. Furthermore, the production and release of microcystin （MC）-LR were investigated. Aluminum silicate, CuSO4, and Emma-11 were more effective than pyrogallic acid in disrupting the cells of M. aeruginosa, thereby increasing the extracellular MC-LR concentration. Aluminum silicate caused the highest extracellular MC-LR concentration of more than 45 mg·L^-1. Biotoxicity was also detected to evaluate the environmental risks of MC-LR release, which were related to the usages of different algicides. Extracellular MC-LR concentration mostly increased when the biotoxicity of algae solution increased. The experiments were also designed to reveal the effects of physical conditions in riverways, such as natural sunlight, aeration and benthal sludge, on MC-LR degradation. These findings indicated that UV rays in sunlight, which can achieve a MC-LR removal efficiency of more than 15%, played an important role in MC-LR degradation. Among all the physical pathways of MC-LR removal, benthal sludge adsorption presented the optimal efficiency at 20%.

关键词： Microcystis aeruginosa MC-LR release Algicides MC-LR degradation Biotoxicity

Collaborative beamforming based on directional perturbation using one bit feedback

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Journal of Systems engineering and Electronics 2016年第3期27卷 549-554页

作者： Haifen Yang Ning Ding Zhi Zheng Shuisheng Lin Zhongpei Zhang Guangjun Li school of Communication & Information engineering University of Electronic Science and Technology of China

A novel collaborative beamforming algorithm is proposed in a wireless communication system with multiple transmitters and one receiver. All transmitters take part in the collaboration and the weighted message is transmitted simultaneously. In order to maximize the beamforming gain, the transmitters use one bit feedback information to adjust the phase offset. It tracks the direction in which the signal strength at the receiver can increase. The directional search and perturbation theory is used to achieve the phase alignment. The feasibility of the proposed algorithm is proved both experimentally and theoretically. Simulation results show that the proposed algorithm can improve the convergent speed of the phase alignment.

关键词： collaborative beamforming one-bit feedback directional perturbation convergent speed

Optimization model analysis of centralized groundwater source heat pump system in heating season

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Frontiers in Energy 2015年第3期9卷 343-361页

作者： Shilei LU Yunfang QI Zhe CAI Yiran LI school of Environmental science and engineering Tianjin University Tianjin 300072 China

The ground-water heat-pump system （GWHP） provides a high efficient way for heating and cooling while consuming a little electrical energy. Due to the lack of scientific guidance for operating control strategy, the coefficient of performance （COP） of the system and units are still very low. In this paper, the running strategy of GWHP was studied. First, the groundwater thermal transfer calculation under slow heat transfixion and transient heat transfixion was established by calculating the heat transfer simulation software Flow Heat and using correction factor. Next, heating parameters were calculated based on the building heat load and the terminal equipment characteristic equation. Then, the energy consumption calculation model for units and pumps were established, based on which the optimization method and constraints were established. Finally, a field test on a GWHP system in Beijing was conducted and the model was applied. The new system operation optimization idea for taking every part of the GWHP into account that put forward in this paper has an important guiding significance to the actual operation of underground water source heat pump.

关键词： optimization model groundwater source heatpump system theoretical analysis example verification,heating season

Identifying influential spreaders in complex networks based on density entropy and community structure

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Chinese Physics B 2024年第5期33卷 765-774页

作者：苏湛陈磊艾均郑雨语别娜 school of Optical-Electrical and Computer engineering University of Shanghai for Science and Technology

In recent years,exploring the relationship between community structure and node centrality in complex networks has gained significant attention from researchers,given its fundamental theoretical significance and practical *** address the impact of network communities on target nodes and effectively identify highly influential nodes with strong propagation capabilities,this paper proposes a novel influential spreaders identification algorithm based on density entropy and community structure(DECS).The proposed method initially integrates a community detection algorithm to obtain the community partition results of the *** then comprehensively considers the internal and external density entropies and degree centrality of the target node to evaluate its *** validation is conducted on eight networks of varying sizes through susceptible–infected–recovered(SIR)propagation experiments and network static attack *** experimental results demonstrate that the proposed method outperforms five other node centrality methods under the same comparative conditions,particularly in terms of information spreading capability,thereby enhancing the accurate identification of critical nodes in networks.

关键词： corrigendum electron impact ionization cross sections carbon monoxide