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The microstructure of a single crystal superalloy after different aging heat treatments

Rare Metals 2018年第3期37卷 210-216页

作者： Xiao-Dai Yue jia-Rong Li Xiao-guang Wang Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials

To study the influence of aging heat treatments on the microstructure of single crystal superalloys with high content of refractory elements and optimal the aging heat treatment regimes, a single crystal superalloy containing 22 wt% refractory elements was *** show that for the experimental alloy, even the homogenization-solution heat treatment for 25 h cannot homogenize the alloying elements completely. During primary aging heat treatment, γ＇ phase grows larger and turns to regular cubes. Higher aging temperature induces larger γ＇ cubes. For specimens with primary aging heat treated at 1120 ℃,γ＇ morphology does not change apparently during secondary aging heat treatment. For specimens with primary aging heat treatment at 1150 ℃,γ＇phase in interdendrite grows obviously comparing with that in dendrites. By analyzing the precipitating kinetics of γ＇phase, it is found that owning to the dendrite segregation and different aging heat treatment temperatures, γ＇ phase at different regions grows under the control of different factors at different aging heat treatment stages. The two controlling factors that are driving forces of phase transformation and element diffusion rate induce obviously different growth rates of γ＇ phase. As a result, the γ＇-precipitating behaviors are variable based on different solute concentrations and aging temperatures. For advanced single crystal superalloys that are supposed to be used at relatively high temperatures, the final γ＇ size after aging heat treatment is suggested to be close to the crossing point of diffusion controlling curve and driving force controlling curve corresponding to the serving temperature. And then,high-temperature properties can be improved.

关键词： Single crystal superalloy Aging heat treatment γ' precipitation Kinetics

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What activates the Mg surface——A comparison of Mg dissolution mechanisms

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Journal of Materials Science & Technology 2020年第22期54卷 204-220页

作者： Jufeng Huang guang-Ling song Andrej Atrens Matthew Dargusch Center for Marine Materials Corrosion and Protection College of MaterialsXiamen UniversityXiamen 361005China State Key Laboratory of Physical Chemistry of Solid Surfaces Xiamen UniversityXiamen 361005China Centre for Advanced Materials Processing and Manufacturing School of Mechanical and Mining EngineeringThe University of QueenslandSt.LuciaQld 4072Australia

Several mechanisms have been proposed to interpret the widely reported phenomenon of Mg corrosion that the hydrogen evolution rate increases with increasing anodic potential or anodic current density. This paper critically analyzed the two main mechanisms,(1) "the incomplete film univalent Mg+ion mechanism" and(2) "the enhanced catalytic activity mechanism", aiming to clarify the current understanding of the Mg corrosion mechanism and to provide a profound insight into the Mg characteristic electrochemical behavior, anodic polarization accelerating both hydrogen evolution and Mg dissolution. It is expected that the deepened fundamental understanding from this comprehensive mechanistic review will provide a basis of practical applications for Mg alloys and open up a new way to the control of corrosion of Mg alloys in practice.

关键词： Magnesium Negative difference effect(NDE) Corrosion Hydrogen evolution Anodic dissolution

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FLOW AROUND A CIRCULAR CYLINDER USING A FINITE-VOLUME TVD SCHEME BASED ON A VECTOR TRANSFORMATION APPROACH

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Journal of Hydrodynamics 2010年第2期22卷 221-228页

作者： WANG jia-song School of Naval Architecture Ocean and Civil Engineering Shanghai Jiao Tong University Shanghai 200240China

Flows around a circular cylinder displaying an unsteady vortex shedding process at the Reynolds numbers of 1000,3900 and 1×104 are studied using a finite-volume Total Variation Diminishing（TVD） scheme for solving the Unsteady Reynolds-Averaged Navier-Stokes（URANS） *** Elemental Velocity Vector Transformation（EVVT） approach is proposed for the local normal and tangential velocity transformation at the interfaces of main and satellite *** presented method is validated by comparing with the available experimental data and numerical *** is shown that the two-dimensional TVD finite volume method with the Renormalization Group（RNG） turbulence model can be used to determine hydrodynamic forces and captures vortex shedding characteristics very well.

关键词： Total Variation Diminishing(TVD) finite volume method Renormalization Group(RNG) turbulence model flow around circular cylinder Elemental Velocity Vector Transformation(EVVT)

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New Delay-dependent Global Asymptotic Stability Condition for Hopfield Neural Networks with Time-varying Delays

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International Journal of Automation and computing 2009年第4期6卷 415-419页

作者： guang-Deng Zong jia Liu Research Institute of Automation Qufu Normal University Qufu 273165 PRC

This paper deals with the global asymptotic stability problem for Hopfield neural networks with time-varying delays. By resorting to the integral inequality and constructing a Lyapunov-Krasovskii functional, a novel delay-dependent condition is established to guarantee the existence and global asymptotic stability of the unique equilibrium point for a given delayed Hopfield neural network. This criterion is expressed in terms of linear matrix inequalities （LMIs）, which can be easily checked by utilizing the recently developed algorithms for solving LMIs. Examples are provided to demonstrate the effectiveness and reduced conservatism of the proposed condition.

关键词： Global asymptotic stability Hopfield neural networks linear matrix inequality (LMI) time-varying delays Lyapunov-Krasovskii functional.

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The differentiability of solutions for elliptic equations which degenerate on part of the boundary of a convex domain

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Applied Mathematics(A Journal of Chinese Universities) 2018年第4期33卷 421-435页

作者： song jia-xin CAO Yi Department of Mathematics and Information Science Shaanxi Normal University

In this paper,we study the differentiability of solutions on the boundary for equartions of type L;u=;u/x;+|x|;;u/y;=f（x,y）,where λ is an arbitrary positive number. By introducing a proper metric that is related to the elliptic operator L;, we prove the differentiability on the boundary when some well-posed boundary conditions are satisfied. The main difficulty is the construction of new barrier functions in this article.

关键词： elliptic equations convex domain differentiability

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Enhanced performance based on cross-layer design from physical to transport layers for multihop wireless networks

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The Journal of China Universities of Posts and Telecommunications 2010年第5期17卷 87-92页

作者： CHEN guang-quan song Mei ZHANG Yong song Jun-de School of Computer Science and Technology Beijing University of Posts and Telecommunications Beijing 100876 China School of Electronic Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

This paper puts forward a novel cognitive cross-layer design algorithms for multihop wireless networks optimization across physical,mediam access control （MAC）,network and transport *** is well known,the conventional layered-protocol architecture can not provide optimal performance for wireless networks,and cross-layer design is becoming increasingly important for improving the performance of wireless *** this study,we formulate a specific network utility maximization （NUM） problem that we believe is appropriate for multihop wireless *** using the dual algorithm,the NUM problem has been optimal decomposed and solved with a novel distributed cross-layer design algorithm from physical to transport *** solution enjoys the benefits of cross-layer optimization while maintaining the simplicity and modularity of the traditional layered *** proposed cross-layer design can guarantee the end-to-end goals of data flows while fully utilizing network *** simulations have evaluated an enhanced performance of the proposed algorithm at both average source rate and network ***,the proposed algorithm has low implementation complexity for practical reality.

关键词： multihop wireless networks cross-layer design optimization distributed algorithm

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The uncertainty propagation analysis of the projectile-barrel coupling problem

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Defence Technology（防务技术） 2017年第4期13卷 229-233页

作者： Lin-fang Qian guang-song Chen Nanjing University of Science & Technology 200 Xiaolingwei Nanjing Jiangsu 210094 China

Based on the model which couples the projectile and gun barrel during an interior ballistic cycle,the uncertainty propagation analysis of the model is presented caused by the uncertainty of the input *** Bootstrap method is employed to calculate the statistical moments(*** mean,variance,skewness coefficient and kurtosis coefficient)of the parameters of the ***,the maximum entropy method is used to estimate the probability density function(PDF)and the cumulative density function(CDF),the interval of the parameters of the projectile are also ***,the results obtained are compared to the results calculated by Monte Carlo(MC)method to verify the effectiveness of the presented ***,the rule and the uncertainty propagation model of the projectile-barrel coupling system are given with the variation of the uncertainties of the input parameters.

关键词： Uncertainty propagation Projectile-barrel coupling Bootstrap Maximum entropy Interval

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A Universal Reduced Rupture Creep Approach for Failure Behavior of Aged Glass Polymers from the Rupture Creep Compliance by the Unified Master Prediction of Long Term Short Term Test of Curved Extrapolation

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Chinese Journal of Chemical Physics 2012年第5期25卷 552-562,I0003页

作者： guang-jun song Da-ming Wu Wei-yue song Ming-shi song Gui-xian Hu School of Mechanical and Electrical EnEineering Beijing University of Chemical Technology BeLying100029 China Department of Polymeric Material Science and Engineering Beijing Institute of Petrochemical Tech-nology Beijing 102617 China School of Materials Science and Engineering Beijing University of Chemical Technology Beijing100029 China

The prediction of long term failure behaviors and lifetime of aged glass polymers from the short term tests of reduced rupture creep compliance （or strain） is one of difficult problems in polymer science and engineering. A new ＂universal reduced rupture creep approach＂ with exact theoretical analysis and computations is proposed in this work. Failure by creep for polymeric material is an important problem to be addressed in the engineering. A universal equation on reduced extensional failure creep compliance for PMMA has been derived. It is successful in relating the reduced extensional failure creep compliance with aging time, temperature, levels of stress, the average growth dimensional number and the parameter in K-W-W function. Based on the universal equation, a method for the prediction of failure behavior, failure strain criterion, failure time of PMMA has been developed which is named as a universal ＂reduced rupture creep approach＂. The results show that the predicted failure strain and failure time of PMMA at different aging times for different levels of stress are all in agreement with those obtained directly from experiments, and the proposed method is reliable and practical. The dependences of reduced extensional failure creep compliance on the conditions of aging time, failure creep stress, the structure of fluidized-domain constituent chains are discussed. The shifting factor, exponent for time-stress superposition at different levels of stress and the shifting factor, exponent for time-time aging superposition at different aging time are theoretically defined respectively.

关键词： Reduced extensional failure creep compliance Extensional failure Predictionof failure strain and time PMMA Shifting factor Shifting exponent

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ESO-KELM-based minor sensor fault identification

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The Journal of China Universities of Posts and Telecommunications 2021年第4期28卷 53-63页

作者： Zhao Kai song jia Wang Xinlong School of Astronautics Beihang UniversityBeijing 100191China

Aiming at the sensor faults of near-space hypersonic vehicles(NSHV), a fault identification method based on the extended state observer and kernel extreme learning machine(ESO-KELM) is proposed in this paper. The method is generated by a combination of the model-based method and the data-driven method. As the source of the fault diagnosis, the residual signals represent the difference between the ESO output and the result measured by the sensor in particular. The energy of the residual signals is distributed in both low frequency bands and high frequency bands. However, the energy of the sensor concentrates on the low-frequency bands. Combined with more different features detected by KELM, the proposed method devotes to improving the accuracy. Meanwhile, it is competent to calculate the magnitude of minor faults based on time-frequency analysis. Finally, the simulation is performed on the longitudinal channel of the Winged-Cone model published by the national aeronautics and space administration(NASA). Results show the validity and the accuracy in calculating the magnitude of the minor faults.

关键词： minor fault diagnosis near-space hypersonic vehicles extended state observer kernel extreme learning machine wavelet packet decomposition

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Preparation and characterization of high-reactivity explosive-based nano-boron microspheres

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Particuology 2024年第10期93卷 125-136页

作者： Chen Dong Yi Wang Kanghui jia Dan song Xiaolan song Chongwei An School of Materials Science and Engineering North University of ChinaTaiyuan030051China Jinxi Group Shanxi jiangyang Chemical Co. Ltd.Taiyuan030051China China Ordnance Institute of Science and Technology Beijing100089China School of Environment and Safety Engineering North University of ChinaTaiyuan030051China

Boron nanoparticles,with their remarkably high gravimetric and volumetric calorific values,emerge as the most promising fuel in energetic ***,challenges such as susceptibility to oxidation,high ignition temperature,and low combustion efficiency have constrained their further *** this study,we fabricated high explosives based nano-boron microspheres with uniform size using the electrostatic spray method,in which the boron nanoparticles and high explosives(CL-20 or PETN)are closely bonded together by fluorinated polymer(F2602)and evenly *** results indicated that the microspheres exhibited high sphericity and showed an enhanced antioxidant *** addition of high-energy explosives not only reduced the thermal oxidation temperature of nano-boron powder within the microspheres but also significantly enhanced the pressurization ***,the microspheres with added high-energy explosives released more energy during the combustion *** to physically mixed samples,electrostatically sprayed microspheres with a uniform microstructure still exhibited higher ***,the design and synthesis of microspheres with controllable structures using the electrostatic spray method show promising application prospects.

关键词： Nano-boron CL-20 PETN Electrospraying Ignition and combustion

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