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Steady-State Creep Behavior of Super304H Austenitic Steel at Elevated Temperatures

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Acta Metallurgica Sinica(English Letters) 2015年第11期28卷 1336-1343页

作者： ping Ou Long Li Xing-fei Xie Jian Sun Shanghai Key Laboratory of Advanced High-Temperature Materials and Precision Forming School of Materials Science and EngineeringShanghai Jiaotong University School of Materials Science and Engineering Jiangxi University of Science and Technology

Creep behavior of Super304H austenitic steel has been investigated at elevated temperatures of 923-973 K and at applied stress of 190-210 MPa. The results show that the apparent stress exponent and activation energy in the creep deformation range from 16.2 to 27.4 and from 602.1 to 769.3 kJ/mol at different temperatures, respectively. These high values imply the presence of a threshold stress due to an interaction between the dislocations and Cu-rich precipitates during creep deformation. The creep mechanism is associated with the dislocation climbing governed by the matrix lattice diffusion. The origin of the threshold stress is mainly attributed to the coherency strain induced in the matrix by Cu-rich precipitates. The theoretically estimated threshold stresses from Cu-rich precipitates agree reasonably with the experi- mental results.

关键词： Super304H steel Cu-rich precipitate Creep Threshold stress

Science Letters:A current-differential-based method for improving dynamic characteristics of electromagnetic actuators

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第9期10卷 1241-1244页

作者： ping fang Qi-peng LI Fan DING State Key Lab of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China School of Mechanical and Automotive Engineering Zhejiang University of Science and Technology Hangzhou 310023 China

This paper presents a new control strategy based on current differential feedback to accelerate the dynamic response of electromagnetic actuators, instead of traditional closed-loop control based on displacement feedback. The method mainly includes a differentiator, proportioner and signal synthesizer. Analysis and simulation on the step characteristics of an electromagnetic actuator were discussed, and all the results show that the approach can improve the actuator's step response greatly. Finally, the control method is applied to a real gravure system which verifies the control performance.

关键词： Electromagnetic actuator Control method Dynamic characteristics Current differential

Effect of Short Chain Alcohols upon Viscosity of TTAB Solution

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Chinese Journal of Chemical Physics 2008年第2期21卷 169-173页

作者： Yun-fei Yan Hua-zhen Li Hai-yang Yang Jia-sheng Qian ping-ping Zhu ping-sheng He Department of Polymer Science and Engineering University of Science and Technology of China Hefei 230026 China

The effect of ethanol （C2H5OH）, propanol （C3H7OH）, and butanol （C4H9OH） upon the viscosity of tetradecyltrimethylammonium bromide （TTAB） solution in the presence or absence of KBr at 30℃was investigated, where the surfactant concentration CS is kept constant. In the absence of KBr, the relative viscosity ηr of TTAB solution increases linearly with the alcohol concentration CA, indicating that the alcohols do not promote micelle formation of TTAB. In the presence of KBr, ηr linearly decreases with CA for C2H5OH, but it exhibits a maximum with increasing CA for C3H7OH or C4H9OH. The facts reveal that C2H5OH or C4H9OH promotes the micelle formation of TTAB. A possible explanation is that the hydrophobicity of the mieellar interior is enhanced by KBr, so that C2H5OH or C4H9OH can dissolve in micelle and promotes micelle formation. In the presence of KCl, which is less efficient in promoting the micelle formation of cationic surfactant, both C3H7OH and C4H9OH have only a slight effect on the micelle formation. In contrast, due to the hydrophilicity, C2H5OH cannot dissolve in micelles in the presence of KBr or KCl.

关键词： Relative viscosity Cationic surfactant Organic additive Hydrophobic interaction

INTERMOLECULAR AND INTRAMOLECULAR INTERACTIONS OF POLYMER GUAR GUM IN SOLUTIONS

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Chinese Journal of Polymer Science 2005年第5期23卷 557-559页

作者： Yun-fei Yan Hai-yang Yang Wen-yong Liu ping-ping Zhu ping-sheng He Department of Polymer Science and Engineering University of Science and Technology of China Hefei 230026 China Structure Research Laboratory University of Science and Technology of China Hefei 230026 China

The tetrahedral borate ion can crosslink with polymer guar gum in aqueous solutions. If the concentration of guar gum is less than 0.045 g/dL, the intramolecular interaction between guar gum and borate ion increases due to the formation of crosslinks. As a result, the polymer chains of guar gum in solution shrink in size and the reduced viscosity of polymer solution decreases accordingly. On the other hand, if the concentration of guar gum is greater than 0.045 g/dL, the intermolecular interaction becomes apparent due to the same reason. The polymer chains, therefore, associate together and the reduced viscosity of polymer solution increases considerably. According to this technique, the critical concentration c^＊, presented by de-Gennes, is determined successfully.

关键词： Guar gum Crosslink reaction Critical concentration c^*.

Grease film evolution in rolling elastohydrodynamic lubrication contacts

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Friction 2021年第1期9卷 179-190页

作者： Xinming LI Feng GUO Gerhard POLL Yang fei ping YANG School of Mechanical and Automotive Engineering Qingdao University of TechnologyQingdao 266250China Institute of Machine Design and Tribology Leibniz University HannoverHannover 30167Germany

Although most rolling element bearings are grease lubricated,the underlying mechanisms of grease lubrication has not been fully *** study investigates grease film evolution with glass disc revolutions in rolling elastohydrodynamic lubrication(EHL)*** evolution patterns of the grease films were highly related to the speed ranges and grease *** transference of thickener lumps,film thickness decay induced by starvation,and residual layer were *** formation of an equilibrium film determined by the balance of lubricant loss and replenishment was *** primary mechanisms that dominate grease film formation in different lubricated contacts were clarified.

关键词： grease lubrication rolling contacts starvation replenishment elastohydrodynamic lubrication(EHL)

First-order primal-dual algorithm for sparse-view neutron computed tomography-based three-dimensional image reconstruction

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Nuclear Science and Techniques 2023年第8期34卷 35-53页

作者： Yang Liu Teng-fei Zhu Zhi Luo Xiao-ping Ouyang School of Nuclear Science and Engineering North China Electric Power UniversityBeijing 102206China State Key Laboratory of Nuclear Resources and Environment East China University of TechnologyNanchang 330013China State Key Laboratory of Intense Pulsed Radiation Simulation and Effect Xi’an 710024China

Neutron computed tomography(NCT)is widely used as a noninvasive measurement technique in nuclear engineering,thermal hydraulics,and cultural *** neutron source intensity of NCT is usually low and the scan time is long,resulting in a projection image containing severe *** reduce the scanning time and increase the image reconstruction quality,an effective reconstruction algorithm must be *** CT image reconstruction,the reconstruction algorithms can be divided into three categories:analytical algorithms,iterative algorithms,and deep *** the analytical algorithm requires complete projection data,it is not suitable for reconstruction in harsh environments,such as strong radia-tion,high temperature,and high *** learning requires large amounts of data and complex models,which cannot be easily deployed,as well as has a high computational complexity and poor ***,this paper proposes the OS-SART-PDTV iterative algorithm,which uses the ordered subset simultaneous algebraic reconstruction technique(OS-SART)algorithm to reconstruct the image and the first-order primal–dual algorithm to solve the total variation(PDTV),for sparse-view NCT three-dimensional *** novel algorithm was compared with other algorithms(FBP,OS-SART-TV,OS-SART-AwTV,and OS-SART-FGPTV)by simulating the experimental data and actual neutron projection *** reconstruction results demonstrate that the proposed algorithm outperforms the FBP,OS-SART-TV,OS-SART-AwTV,and OS-SART-FGPTV algorithms in terms of preserving edge structure,denoising,and suppressing artifacts.

关键词： NCT First-order primal-dual algorithm OS-SART Total variation Sparse-view

Ammonia removal from low-strength municipal wastewater by powdered resin combined with simultaneous recovery as struvite

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Frontiers of Environmental Science & Engineering 2021年第1期15卷 125-134页

作者： Kuo fang fei Peng Hui Gong Huanzhen Zhang Kaijun Wang State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing 100084China School of Water Resources&Environment China University of GeosciencesBeijing 100083China

Low-strength municipal wastewater is considered to be a recoverable nutrient resource with economic and environmental ***,various technologies for nutrient removal and recovery have been *** this paper,powdered ion exchange resin was employed for ammonia removal and recovery from imitated low-strength municipal *** effects of various working conditions(powdered resin dosage,initial concentration,and pH value)were studied in batch experiments to investigate the feasibility of the approach and to achieve performance *** maximum adsorption capacity determined by the Langmuir model was 44.39 mg/g,which is comparable to traditional ion exchange ***,the effects of co-existing cations(Ca^(2+),Mg^(2+),K^(+))were *** on the above experiments,recovery of ammonia as struvite was successfully achieved by a proposed two-stage crystallization process coupled with a powdered resin ion exchange *** electron microscopy(SEM)and X-ray diffractometry(XRD)results revealed that struvite crystals were successfully gained in alkaline conditions(pH=10).This research demonstrates that a powdered resin and two-stage crystallization process provide an innovative and promising means for highly efficient and easy recovery from low-strength municipal wastewater.

关键词： Ammonia removal and recovery Powdered resin Crystallization process Struvite Co-existing cations

3D robust anisotropic diffusion filtering algorithm for sparse view neutron computed tomography 3D image reconstruction

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Nuclear Science and Techniques 2024年第3期35卷 13-29页

The most critical part of a neutron computed tomography(NCT) system is the image processing algorithm,which directly affects the quality and speed of the reconstructed *** types of noise in the system can degrade the quality of the reconstructed ***,to improve the quality of the reconstructed images of NCT systems,efficient image processing algorithms must be *** anisotropic diffusion filtering(ADF) algorithm can not only effectively suppress the noise in the projection data,but also preserve the image edge structure information by reducing the diffusion at the image ***,we propose the application of the ADF algorithm for NCT image *** compare the performance of different algorithms in NCT systems,we reconstructed images using the ordered subset simultaneous algebraic reconstruction technique(OS-SART) algorithm with different regular terms as image processing *** the iterative reconstruction,we selected two image processing algorithms,the Total Variation and split Bregman solved total variation algorithms,for comparison with the performance of the ADF ***,the filtered back-projection algorithm was used for comparison with an iterative *** reconstructing the projection data of the numerical and clock models,we compared and analyzed the effects of each algorithm applied in the NCT *** on the reconstruction results,OS-SART-ADF outperformed the other algorithms in terms of denoising,preserving the edge structure,and suppressing *** example,when the 3D Shepp–Logan was reconstructed at 25 views,the root mean square error of OS-SART-ADF was the smallest among the four iterative algorithms,at only *** universal quality index,mean structural similarity,and correlation coefficient of the reconstructed image were the largest among all algorithms,with values of 0.9877,0.9878,and 0.9887,respectively.

关键词： NCT OS-SART Sparse-view Anisotropic diffusion filtering

Enhancing high-temperature tensile properties of Ni/Ni-W laminated composites for MEMS devices

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Journal of Materials Science & Technology 2023年第7期138卷 129-137页

作者： Zhe-Xuan Wang fei Liang Guang-ping Zhang Bin Zhang Key Laboratory for Anisotropy and Texture of Materials Ministry of EducationSchool of Materials Science and EngineeringNortheastern UniversityShenyang 110819China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

There is an increasing demand for materials with excellent mechanical performance for Micro-Electro-Mechanical System(MEMS)devices serving at elevated ***,how to enhance the high-temperature strength of the materials without losing their plasticity is a pending ***,the Ni/Ni-W laminated composites with different monolayer thicknesses and the same ratio of the constituent layer thicknesses were fabricated successfully by using the dual-bath electrodeposition *** microstructure stability and tensile properties of annealed Ni/Ni-W laminated composites with different monolayer thicknesses were investigated at 400℃.The results show that the annealed Ni0.5/Ni-W0.05 laminated composites have both high yield strength(450 MPa)and excellent elongation to failure(25.1%)at 400℃,being superior to that of the monotonic Ni(179 MPa and 17.7%).Such a high strength of the laminated composite at 400℃ results from the contribution of the intrinsically high strength of the Ni-W layers with excellent thermal stability,the thickness-constrained effect on grain growth of Ni layers and the interface coupling effect of heterogeneous *** good plasticity may be derived from the heterogeneous laminated structure and the decrease in the constituent layer thickness,providing a good co-deformation *** mechanisms for the high tensile strength and good plasticity of the Ni/Ni-W laminated composites at 400℃ were analyzed *** findings reveal a potential strategy to fabricate MEMS components with excellent high-temperature tensile properties through tailoring the microstructure thermal stability and the constituent layer scale.

关键词： Laminated composites MEMS Strength Plasticity High temperature