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Enhancement of Sinter Densification of SrO-BaO-Nb_2O_5-SiO_2 Tungsten-Bronze Glass-Ceramics by Doping with P_2O_5

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Journal of Materials Science & Technology 2013年第8期29卷 731-736页

作者： J.C.Chen y.Zhang Shenyang Research and Development Centre for Advanced Materials Institute of Metal ResearchChinese Academy of Sciences State Key Laboratory of New Ceramics and Fine Processing Institute of Nuclear and New Energy TechnologyTsinghua University

Densification behaviors of SrO-BaO-Nb2O5-SiO2 based glass-ceramics prepared by conventional sintering were investigated with an emphasis on the influence of P2O5 content. Although P2O5 dopant did not modify the surface crystallization mechanism, it resulted in a decrease of the glass transition temperature, which facilitates the viscous glass flow necessary for sintering. However, premature crystallization of （Sr, Ba）Nb2O6 induced by addition of excess amount of P2O5 essentially retarded sintering due to the formation of closed pores in the matrix. The SrO-BaO-Nb2O5-SiO2 glass with 1.0 mol% P2O5 （SBN-1P） showed the best sinter densification, which was accomplished at about 850 ℃.

关键词： Sintering densification DieLectric properties Glass-ceramic

Proper orthogonal decomposition analysis of coherent motions in a turbulent annular jet

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Applied Mathematics and Mechanics(English Edition) 2021年第9期42卷 1297-1310页

作者： y.Zhang M.VANIERSCHOT Department of Mechanical Engineering Group T Leuven CampusCelestijnenlaan 300Leuven B-3001Belgium

A three-dimensional incompressible annular jet is simulated by the large eddy simulation(LES)method at a Reynolds number Re=8500.The time-averaged velocity field shows an asymmetric wake behind the central bluff-body although the flow geometry is symmetric.The proper orthogonal decomposition(POD)analysis of the velocity fluctuation vectors is conducted to study the flow dynamics of the wake flow.The distribution of turbulent kinetic energy across the three-dimensional POD modes shows that the first four eigenmodes each capture more than 1%of the turbulent kinetic energy,and hence their impact on the wake dynamics is studied.The results demonstrate that the asymmetric mean flow in the near-field of the annular jet is related to the first two POD modes which correspond to a radial shift of the stagnation point.The modes 3 and 4 involve the stretching or squeezing effects of the recirculation region in the radial direction.In addition,the spatial structure of these four POD eigenmodes also shows the counter-rotating vortices in the streamwise direction downstream of the flow reversal region.

关键词： coherent structure proper orthogonal decomposition(POD) turbulent annular jet large eddy simulation(LES)

Alloy solidification: Assessment and improvement of an easy-to-apply model

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Journal of Materials Science & Technology 2022年第35期130卷 1-11页

作者： H.Liu y.Liu S.L.Lu y.Zhang H.Chen y.Chen M.Qian School of Materials Science and Engineering Southwest Jiaotong UniversityChengdu 610031China Centre for Additive Manufacturing School of EngineeringRMIT UniversityMelbourneVIC 3000Australia School of Materials Science and Engineering Sichuan UniversityChengdu 610065China

It has been a central task of solidification research to predict solute microsegregation. Apart from the Lever rule and the Scheil-Gulliver equation, which concern two extreme cases, a long list of microsegregation models has been proposed. However, the use of these models often requires essential experimental input information, e.g., the secondary dendrite arm spacing(λ), cooling rate( ˙T) or actual solidification range(△T). This requirement disables these models for alloy solidification with no measured values for λ,˙T and △T. Furthermore, not all of these required experimental data are easily obtainable. It is therefore highly desirable to have an easy-to-apply predictive model that is independent of experimental input,akin to the Lever rule or Scheil-Gulliver model. Gong, Chen, and co-workers have recently proposed such a model, referred to as the Gong-Chen model, by averaging the solid fractions(f_(s)) of the Lever rule and Scheil-Gulliver model as the actual solid fraction. We provide a systematic assessment of this model versus established solidification microsegregation models and address a latent deficiency of the model, i.e.,it allows the Lever rule solid fraction fsto be greater than one(f_(s)> 1). It is shown that the Gong-Chen model can serve as a generic model for alloy solidification until fsreaches about 0.9, beyond which(f_(s)> 0.9) its applicability is dictated by both the equilibrium solute partition coefcient(k) and the solute diffusion coefcient in the solid(Ds), which has been tabulated in detail.

关键词： Solidification Microsegregation Solute Back diffusion Eutectic formation

Frequency equations of nonlocal elastic micro/nanobeams with the consideration of the surface effects

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Applied Mathematics and Mechanics(English Edition) 2018年第8期39卷 1089-1102页

作者： H.S.ZHAO y.Zhang S.T.LIE School of Civil and Environmental Engineering Nanyang Technological University

A nonlocal elastic micro/nanobeam is theoretically modeled with the consideration of the surface elasticity, the residual surface stress, and the rotatory inertia,in which the nonlocal and surface effects are considered. Three types of boundary conditions, i.e., hinged-hinged, clamped-clamped, and clamped-hinged ends, are examined. For a hinged-hinged beam, an exact and explicit natural frequency equation is derived based on the established mathematical model. The Fredholm integral equation is adopted to deduce the approximate fundamental frequency equations for the clamped-clamped and clamped-hinged beams. In sum, the explicit frequency equations for the micro/nanobeam under three types of boundary conditions are proposed to reveal the dependence of the natural frequency on the effects of the nonlocal elasticity, the surface elasticity, the residual surface stress, and the rotatory inertia, providing a more convenient means in comparison with numerical computations.

关键词： Fredholm integral equation micro/nanobeam natural frequency nonlocal elasticity surface effect

Generalized canonical transformation for second-order Birkhoffian systems on time scales

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Theoretical & Applied Mechanics Letters 2019年第6期9卷 353-357页

作者： y.Zhang X.H.Zhai college of civil engineering suzhou university of science and technologysuzhou 215011china school of science nanjing university of science and technologynanjing 210094china

The theory of time scales,which unifies continuous and discrete analysis,provides a powerful mathematical tool for the study of complex dynamic systems.It enables us to understand more clearly the essential problems of continuous systems and discrete systems as well as other complex systems.In this paper,the theory of generalized canonical transformation for second-order Birkhoffian systems on time scales is proposed and studied,which extends the canonical transformation theory of Hamilton canonical equations.First,the condition of generalized canonical transformation for the second-order Birkhoffian system on time scales is established.Second,based on this condition,six basic forms of generalized canonical transformation for the second-order Birkhoffian system on time scales are given.Also,the relationships between new variables and old variables for each of these cases are derived.In the end,an example is given to show the application of the results.

关键词： Birkhoffian systems Generalized canonical transformation Time scales calculus Generating function

Electron tomography for sintered ceramic materials by a neural network algebraic reconstruction technique

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Journal of Materials Science & Technology 2022年第5期100卷 75-81页

作者： R.H.Shen y.T.He W.Q.Ming y.Zhang X.D.Xu J.H.Chen Centre for High Resolution Electron Microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China

The missing wedge effect in electron tomography introduces various types of artifacts in the tomograms and lowers the reconstruction resolution and quality.The artifacts produced in tomographic reconstruction of bulk materials can be very severe,particularly for sintered bulk ceramic materials in which there are often nano-pores or pore-like microstructure features.Here,we report a neural network algebraic reconstruction algorithm with no prior knowledge to perform electron tomography for a sintered SiC material with nano carbon zones.The results show that the proposed algorithm has a great suppressive effect on the missing wedge artifacts and a high tolerance for noise.The information in the missing wedge can be partly recovered by this technique.Thus,both the shape of the bulk SiC specimen and its irregular inner pore-like features are correctly retrieved in the obtained 3D image.Our study shows the effectiveness of the neural network algorithm for improving the reconstruction accuracy of electron tomography,in order to reveal sophisticated 3D microstructures generally existing in sintered ceramic materials.

关键词： Neural network Missing wedge Electron tomography Sintered ceramics

Attitude control for part actuator failure of agile small satellite

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Acta Mechanica Sinica 2008年第4期24卷 463-468页

作者： J.R.zhang A.Rachid y.Zhang Beijing Institute of Technology School of Aerospace Science and Engineering 100081 Beijing China Univercite de Picardie-Jules Veme 80000 Amiens France

The stability and singularity problem of agile small satellite （ASS） with actuator failure is discussed in this paper. Firstly, the three-axis stabilized controller of an ASS is designed, where micro control moment gyros （MCMG＇s） in pyramid configuration （PC） is used as the actuator. By using the same controller and steering law, the control results before and after one gyro fails are compared by simulation. The variation of singular momentum envelope before and after one gyro fails is also compared. The simulation results show that the failure intensively decreases the capacity of output torque, which leads to the emergence of more singular points and the rapid saturation of MCMG＇s. Finally, the parameters of system controller are changed to compare the control effect.

关键词： Micro control moment gyros （MCMG＇s） · Gyro failure ·Singularity analysis · Agile small satellite

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质谱蛋白质组学在临床应用中的机遇和挑战

中华检验医学杂志 2023年第8期46卷 775-779页

作者： Putuma P.Gqamana Brandy L.young Victoria y.Zhang 罗切斯特大学医学中心病理学和检验医学罗切斯特美国

质谱技术作为免疫分析方法的补充,在临床实验室占据重要位置。随着质谱技术在蛋白质组学研究中的应用和发展,临床实验室开始了从小分子检测到蛋白质/多肽检测的探索,逐渐在临床应用的蛋白分析包括甲状腺球蛋白、胰岛素样生长因子-Ⅰ、... 详细信息

质谱技术作为免疫分析方法的补充,在临床实验室占据重要位置。随着质谱技术在蛋白质组学研究中的应用和发展,临床实验室开始了从小分子检测到蛋白质/多肽检测的探索,逐渐在临床应用的蛋白分析包括甲状腺球蛋白、胰岛素样生长因子-Ⅰ、载脂蛋白E和淀粉样蛋白等。然而在发展的道路上,面临前处理优化耗时长、成本高、缺少参考物质、监管不完善等挑战。尽管新兴的蛋白质组学生物标志物转化到临床诊断应用较慢,但庞大的蛋白质组学数据库和蛋白组学研究为后续临床发展提供了有力支撑。

关键词：质谱分析法实验室自建检测蛋白质组学挑战

Fatigue Properties Improvement of Low-Carbon Alloy Axle Steel by Induction Hardening and Shot Peening:A Prospective Comparison

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Acta Metallurgica Sinica(English Letters) 2022年第8期35卷 1343-1356页

作者： G.C.Chu F.Z.Hu X.J.jin y.Zhang Q.Wang J.P.Hou Z.F.zhang Shi-Changxu Innovation Center for Advanced Material Institute of Metal ResearchChinese Academy of SciencesShenyang 110016.China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China Manshan Iron and Steel Co. Ltd.Maanshan 243000China School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Baowu Group Masteel Rail Transit Materials Technology Company Limited Maanshan 243000China

Fatigue fracture is the major threat to the railway axle, which can be avoided or delayed by surface strengthening. In this study, a low-carbon alloy axle steel with two states was treated by surface induction hardening and shot peening, respectively, to reveal the mechanism of fatigue property improvement by microstructure characterization, microhardness measurement, residual stress analysis, roughness measurement, and rotary bending fatigue tests. The results indicate that both quenching and tempering treatment can effectively improve the fatigue properties of the modified axle steel. In addition, induction hardening can create an ideal hardened layer on the sample surface by phase transformation from the microstructure of ferrite and pearlite to martensite. By comparison, shot peening can modify the microstructure in surface layer by surface severe plastic deformation introducing a large number of dislocation and even cause grain refinement. Both induction hardening and shot peening create compressive residual stress into the surface layer of axle steel sample, which can effectively reduce the stress level applied to the metal surface during the rotary bending fatigue tests. On the whole, the contribution of induction hardening to the fatigue life of axle steel sample is better than that of the shot peening, and induction hardening shows obvious advantages in improving the fatigue life of axle steel.

关键词： Surface strengthening Induction hardening Shot peening Axle steel Fatigue property improvement