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Solvo-thermal synthesis and characterization of nest-like zinc oxide

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中国有色金属学会会刊：英文版 2010年第1期20卷 119-122页

作者：李酽凤慧云张楠刘传生 College of Science Civil Aviation University of China

With Zn(NO3)2·6H2O and NaOH as starting materials, a novel nest-like ZnO nanostructure was successfully synthesized by a solvo-thermal method. The products were characterized by X-ray diffraction, photoluminescence and scanning electron microscopy. The growth mechanism of the nest-like ZnO was discussed. The results show that the as-synthesized samples have a wurtzite structure, with a weak UV emission at about 395 nm, a green emission at around 557 nm and a blue-green emission at 453 nm. SEM investigation reveals that the growth route of the nest-like ZnO can be considered involving three stages: nano-sized ZnO sheet can be firstly achieved, then outspreads quickly and increasingly becomes a long fishbone-like strip with many branch sheets, and finally these sheets curl into a nest-like structure.

关键词：氧化锌热合成表征扫描电子显微镜巢纳米结构绿光发射 X射线衍射

Preparation and characterization of CeO_2 doped ZnO nano-tubes fluorescent composite

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Journal of Rare Earths 2010年第4期28卷 571-575页

作者：李酽刘秀琳栗建钢 College of Science Civil Aviation University of China

ZnO nanotubes were hydrothermally synthesized and the ZNTs/CeO2 fluorescent composite were prepared by introducing nano CeO2 particles into ZnO nano-tubes via a chemical solution adsorption and annealing process. The samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transformation infrared spectroscopy and room temperature photoluminescence measurement. Due to the interaction between Ce4+ and the surface atoms of ZnO2 nano-tubes, a photoluminescence enhancement was obser...

关键词： chemical synthesis inorganic compounds Fourier transform infrared spectroscopy photoluminescence spectroscopy rare earths

Fractional variant of Stokes–Einstein relation in aqueous ionic solutions under external static electric fields

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Chinese Physics B 2020年第3期29卷 323-329页

作者： Gan Ren Shikai Tian departments of Physics&Key Laboratory of Photonic and Optical Detection in civil aviation Civil Aviation Flight University of ChinaGuanghan 618307China

Both ionic solutions under an external applied static electric field E and glassy-forming liquids under undercooled state are in non-equilibrium *** this work,molecular dynamics(MD)simulations with three aqueous alkali ion chloride(NaCl,KCl,and RbCl)ionic solutions are performed to exploit whether the glass-forming liquid analogous fractional variant of the Stokes–Einstein relation also exists in ionic solutions under *** results indicate that the diffusion constant decouples from the structural relaxation time under E,and a fractional variant of the Stokes–Einstein relation is observed as well as a crossover analogous to the glass-forming liquids under *** fractional variant of the Stokes–Einstein relation is attributed to the E introduced deviations from Gaussian and the nonlinear effect.

关键词： ionic solutions Stokes–Einstein relation non-equilibrium steady state molecular dynamics simulation

Brine-freeze-thaw Durability and Crack Density Model of Concrete in Salt Lake Region

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Journal of Wuhan University of Technology(Materials Science) 2020年第3期35卷 561-570页

作者： GONG Wei YU Hongfa MA Haiyan HAN Wenliang department of civil aviation Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The brine-freeze-thaw durability (defined as the durability under freeze-thaw cycles in Qinghai salt lake brine) of concrete (ordinary Portland cement concrete (OPC), high performance concrete (HPC-a), high performance concrete with steel fiber (HPC-b), and high performance concrete with high Young's modulus polyethylene fiber (HPC-c)) was systematically investigated by the relative dynamic elastic modulus, the relative mass, the appearance, the scanning electron microscopy, and the X-ray diffraction. In addition, the low-temperature physical and chemical corrosion mechanism and a crack density model after the modified relative dynamic elastic modulus being taken into consideration were proposed. The results show that the deterioration of OPC is the severest, followed by HPC-a, HPC-c and HPC-b. The admixture or the fiber is mixed into concrete, which can improve the brine-freeze-thaw durability of concrete. The critical mass growth of the failure of concrete is 3.7%. The cause of the deterioration of concrete under the brine-freeze-thaw cycles is physical and chemical corrosion, not freezing and thawing. The crack density model can effectively describe the deterioration evolution of concrete.

关键词： brine-freeze-thaw durability relative dynamic elastic modulus relative mass micro-analysis modeling

A large-scale flight multi-objective assignment approach based on multi-island parallel evolution algorithm with cooperative coevolutionary

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Science China(Information Sciences) 2016年第7期59卷 185-201页

作者： Renli L Xiangmin GUAN Xueyuan LI Inseok HWANG department of General aviation Civil Aviation Management Institute of China School of Electronic and Information Engineering Beihang University School of Aeronautics and Astronautics Purdue University

Due to the rapid increase of air traffic demand, the large-scale flight assignment plays a crucial role in reducing airspace congestion and economic losses via reasonably regulating the air traffic flow of China. In this paper, the large-scale flight assignment problem is formulated as a multi-objective model with consideration of the reduction of airspace congestion and flight delay. However, it is a large-scale combinatorial optimization problem with complex constraints and tightly coupled decision variables, which is difficult to deal ***, an effective multi-objective optimization algorithm is proposed based on the multi-island parallel evolution framework(PEA) with a left-right probability migration topology. Multi-island PEA employs multiple evolution populations for solving the problem simultaneously, and the left-right probability migration topology for exchange individuals among populations to improve the efficiency of the cooperation of populations. Then the cooperative co-evolution(CC) algorithm is introduced for each population to further improve the searching capability. Simulation results using the real traffic data from the China air route network and daily flight plans demonstrate that the proposed approach can improve the solution quality effectively, showing superiority to the existing approaches such as the multi-objective genetic algorithm, the well-known multi-objective evolutionary algorithm based on decomposition, a CC-based multi-objective algorithm as well as other two parallel evolution algorithms with different migration topologies.

关键词： air traffic flow management flight assignment multi-island parallel evolution algorithm migration topology cooperative co-evolution

Dynamic crossover in [VIO^(2+)][Tf_(2)N-]_(2) ionic liquid

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Chinese Physics B 2021年第1期30卷 374-379页

作者： Gan Ren departments of Physics&Key Laboratory of Photonic and Optical Detection in civil aviation Civil Aviation Flight University of ChinaGuanghan 618307China

Ionic liquids usually behave as fragile liquids,and the temperature dependence of their dynamic properties obeys supper-Arrhenius *** this work,a dynamic crossover is observed in([VIO^(2+)][Tf_(2)N-]_(2)) ionic liquid at the temperature of 240-800 *** diffusion coefficient does not obey a single Arrhenius law or a Vogel-Fulcher-Tammann(VFT) relation,but can be well fitted by three Arrhenius laws or a combination of a VFT relation and an Arrhenius *** origin of the dynamic crossover is analyzed from correlation,structure,and *** gets a stronger backward correlation at a lower temperature,as shown by the fractal dimension of the random *** temperature dependence function of fractal dimension,heterogeneity order parameter,and thermodynamic data can be separated into three regions similar to that observed in the diffusion *** two crossover temperatures observed in the three types of data are almost the same as that in diffusion coefficient fitted by three Arrhenius *** results indicate that the dynamic crossover of[VIO2+][Tf2 N-]2 is attributed to the heterogeneous structure when it undergoes cooling.

关键词： ionic liquids dynamic crossover heterogeneity order parameter fractal dimension fragile

Generalized mixed finite element method for 3D elasticity problems

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Acta Mechanica Sinica 2018年第2期34卷 371-380页

作者： Guanghui Qing Junhui Mao Yanhong Liu College of Aeronautical Engineering Civil Aviation University of China

Without applying any stable element techniques in the mixed methods, two simple generalized mixed element(GME) formulations were derived by combining the minimum potential energy principle and Hellinger–Reissner(H–R) variational principle. The main features of the GME formulations are that the common C0-continuous polynomial shape functions for displacement methods are used to express both displacement and stress variables, and the coefficient matrix of these formulations is not only automatically symmetric but also invertible. Hence, the numerical results of the generalized mixed methods based on the GME formulations are stable. Displacement as well as stress results can be obtained directly from the algebraic system for finite element analysis after introducing stress and displacement boundary conditions simultaneously. Numerical examples show that displacement and stress results retain the same accuracy. The results of the noncompatible generalized mixed method proposed herein are more accurate than those of the standard noncompatible displacement method. The noncompatible generalized mixed element is less sensitive to element geometric distortions.

关键词： Minimum potential energy principle Hellinger–Reissner (H–R) variational principle Generalized variational principle Generalized mixed element (GME) Elasticity problem Noncompatible mode

Highly accurate symplectic element based on two variational principles

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Acta Mechanica Sinica 2018年第1期34卷 151-161页

作者： Guanghui Qing Jia Tian College of Aeronautical Engineering Civil Aviation University of China

For the stability requirement of numerical resultants, the mathematical theory of classical mixed methods are relatively complex. However, generalized mixed methods are automatically stable, and their building process is simple and straightforward. In this paper, based on the seminal idea of the generalized mixed methods, a simple, stable, and highly accurate 8-node noncompatible symplectic element(NCSE8) was developed by the combination of the modified Hellinger-Reissner mixed variational principle and the minimum energy principle. To ensure the accuracy of in-plane stress results, a simultaneous equation approach was also suggested. Numerical experimentation shows that the accuracy of stress results of NCSE8 are nearly the same as that of displacement methods, and they are in good agreement with the exact solutions when the mesh is relatively fine. NCSE8 has advantages of the clearing concept, easy calculation by a finite element computer program, higher accuracy and wide applicability for various linear elasticity compressible and nearly incompressible material problems. It is possible that NCSE8 becomes even more advantageous for the fracture problems due to its better accuracy of stresses.

关键词： Modified H-R mixed variational principle Partial-mixed element Noncompatible symplectic element Finite element method Nearly incompressible material

Accuracy analysis of a single-fault Markov model for FADEC system

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Journal of Systems Engineering and Electronics 2019年第5期30卷 1044-1052页

作者： CAI Jing HU Wei CAI Kunye College of civil aviation Nanjing University of Aeronautics and Astronautics

Time-limited dispatching(TLD)analysis of the full authority digital engine control(FADEC)systems is an important part of the aircraft system safety analysis and a necessary task for the certification of commercial aircraft and *** the time limited dispatch guidance document ARP5107B,a single-fault Markov model(MM)approach is proposed for TLD ***,ARP5107B also requires that the loss of thrust control(LOTC)rate error calculated by applying the single-fault MM must be less than 5%when performing airworthiness ***,the sources of accuracy errors in three kinds of MM are analyzed and specified through a case study of the general FADEC system,and secondly a two-fault MM considering maintenance policy is established through analyzing and calculating the expected repair time when two related faults ***,a specific FADEC system is given to study on the influence factors of accuracy error in the single-fault MM,and the results show that the accuracy error of the single-fault MM decreases with the increase of short or long prescribed dispatch time,and the range values of short time(ST)and long time(LT)are determined to satisfy the requirement of accuracy error within 5%.

关键词： full authority digital engine control(FADEC)system Markov model(MM) accuracy analysis loss of thrust control(LOTC)