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Development and Oxidation Behavior of Al-Cu-Fe Quasicrystalline Coating on Ti Alloy

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Journal of Materials science & Technology 2004年第6期20卷 713-715页

作者： Fei CAI, Chungen ZHOU, Huibin XU and Shengkai GONGDepartment of Materials science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China Dept. of Mat. Sci. and Eng. Beijing Univ. of Aero. and Astron. Beijing 100083 China

An oxidation resistant Al-Cu-Fe quasicrystalline coating was fabricated on substrate of Ti alloy by low pressure plasma spraying (LPPS) method. As-sprayed Al-Cu-Fe coating has a rapidly solidified lamellar microstructure consisting of quasicrystalline phase and crystalline phase. The formation of quasicrystalline coating is related to the annealing. The results from the ox!dat!on experiments showed that Al-Cu-Fe quasicrystalline coating improved the oxidation resistance of Ti-base alloys. During the oxidation period there is no evident spallation of the coating from the substrate. Oxide formed on the surface of Al-Cu-Fe quasicrystalline coating after oxidation consisted of Al2O3. Oxidation occurs Ieading to a change of concentration and phase transformation in the coating surface. Selective oxidation of AI transforms the quasicrystalline phase into the phase.

关键词： Low pressure plasma spray Ti-base alloy Al-Cu-Fe quasicrystal Oxidation Coating

Finite-time adaptive sliding mode control for heavyweight airdrop operations

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Journal of Systems Engineering and Electronics 2017年第2期28卷 338-346页

作者： Ri Liu Xiuxia Sun Wenhan Dong Dong Wang Aeronautics and Astronautics Engineering College Air Force Engineering University Xi’an 710038 China

This paper investigates the problem of designing a fast convergent sliding mode flight controller of a transport aircraft for heavyweight airdrop operations in the presence of bounded uncertainties without the prior knowledge of the bounds. On the basis of feedback linearization of the aircraft-cargo motion system, a novel integral sliding mode flight control law with gains adaptation is proposed. It contains a nominal control law used to achieve finite-time stabilization performance and a compensated control law used to reject the uncertainties. The switching gains of the compensated control law are tuned using adaptation algorithms, and the knowledge of the bounds of the uncertainties is not required to be known in advance. Meanwhile, the severe chattering of the sliding mode control that caused by high switching gains is effectively reduced. The controller and its performance are evaluated on a transport aircraft performing a maximum load airdrop task in a number of simulation scenarios.

关键词： flight control nonlinear system sliding mode control adaptive control finite-time stability

Annealing Effect on Mechanical Properties of Ti_(51)Ni_(13)Pd_(36)High Temperature Memory Alloy

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Journal of Materials science & Technology 2000年第5期16卷 531-533页

作者： Xu, HB Hu, SQ Jiang, CB Gong, SK Beijing Univ Aeronaut & Astronaut Dept Mat Sci & Engn Beijing 100083 Peoples R China

The high temperature shape memory alloy Ti51Ni13Pd36 was subjected to a cold working and annealing treatment to improve its mechanical properties and the shape memory effect. It was found that recovery of the cold worked alloys started at near 673 K and the recrystallization temperature was at about 748 K. The grain size decreased with the increase of annealing temperature below 923 K and then increased when above 923 K. The smallest average grain size of about 3.5μm, which is approximately 10 times smaller than the hot rolled one, permitted the best combination of the mechanical properties in the alloy annealed at 923 K for 1h. The cold rolling raised the peak temperature of reverse transformation. This temperature dropped very sharply when the specimen was annealed at temperatures higher than 673 K.

关键词： Alloys

Microstructure and properties of electroformed nickel under different waveform conditions

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Rare Metals 2023年第1期42卷 320-326页

作者： Jing Li Jian-Gang Qian Xiao-Tian Hu Tie-Jun Li Hai-Ting Li School of Chemistry and Environment Beihang UniversityBeijing100191China

In order to prepare electroformed nickel with excellent properties,the effect of different waveforms on microstructure and mechanical properties was investigated by optical microscopy(OM),X-ray diffraction(XRD) and tensile test,*** results show that the samples are composed of micron columnar grains with high-density nanoscale coherent twin boundaries which are parallel to the growth *** tensile strength and elongation display opposite tendency with the increase in current density when direct current(DC) electroforming was ***,under the condition of pulse current(unidirectional,bidirectional) electroforming,the change regulation of tensile strength and elongation is close while cathode(peak,positive peak) current density *** results show that electroformed nickel layers with high purity are all fcc crystal configuration under different conditions of the current *** nickel layers formed under bidirectional pulse current behave superior global performance with tensile strength of 692.0 MPa and elongation of 27.6 %.

关键词： Current waveform Electroformed nickel Organization Mechanical properties

Image separation using wavelet-complex shearlet dictionary

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Journal of Systems Engineering and Electronics 2014年第2期25卷 314-321页

作者： Shuaiqi Liu Shaohai Hu Yang Xiao Institute of Information science Beijing Jiaotong University Beijing Key Laboratory of Advanced Information science and Network Technology

This paper presents a new method for image separation through employing a combined dictionary consisting of wavelets and complex shearlets. Because the combined dictionary sparsely represents points and curvilinear singularities respectively, the image can be decomposed into pointlike and curvelike parts as accurate as possible. The proposed method based on the geo- metric separation theory introduced by Donoho in 2005 shows that accurate geometric separation of the morphologically distinct fea- tures of points and curves can be achieved by l1 minimization. The experimental results show that the proposed method can not only be effective but also greatly reduce the computing time.

关键词： geometric separation l1 minimization sparse approx-imation complex shearlet.

Aging microstructural characteristics of ZA-27 alloy and SiC_p/ZA-27 composite

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中国有色金属学会会刊：英文版 2006年第1期16卷 98-104页

作者：李子全周衡志骆心怡汪涛沈凯 College of Materials science and Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

The aging characteristics of as-quenched microstructures of ZA-27 alloy and SiCp/ZA-27 composite(ZMCp) were investigated using SEM, EDS and TEM. The structure, morphology and size of sub-grains in primary dendrite in ZMCp continuously change during aging process. Little tiny spherical Zn-rich η phase distributes in the dendrite. Amount of transitional α′phase, well coherent with equilibrium αf phase, in SiCp-neighboring dendrite edge zone is less than that in dendrite center zone. Both eutectic and peritectic β phase transform into lamellar α and η phases, obeying [ 2113]η∥[110]α, and (002)α∥ (1 101)η. In the like-eutecticum of ZMCp, less amount of β phase and decomposition products are found. The size of α phase decomposed from peritectic β phase in ZMCp is obviously larger than that in the monolithic alloy. The lamella decomposition of β phase beside SiCp is evidently more rapid than that in the alloy. SiC particulates strongly accelerate neighboring β phase decomposition in aging process.

关键词：金属基复合材料碳化硅 SEM EDS TEM 显微结构

Robust Strict Positive Real Stabilization for Uncertain Systems

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science China Mathematics 1993年第1期36卷 117-128页

作者：贾英民高为炳程勉 The 7th Research Division Beijing University of Aeronautics & Astronautics

This paper is devoted to the study of robust strict positive real stabilization for uncertain systems, i.e. considering how to design a single controller which can not only robustly stabilizes a plant with uncertainties under unity-feedback but also makes the closed-loop system robustly strictly positive real. Though this problem is of important significance in robust control, adaptive control and network theory, it has not had more attention up to now. This paper covers the following problems: (1) Robust strict positive real stabilization criteria for uncertain systems are established. (2) The synthesis approach of a controllet is given, (3) Some applications to the asymptotic hyperstability robustness of nonlinear systems are introduced simply.

关键词： robust control strict positive realness uncertain systems system stabilization.

Artificial bee colony algorithm with comprehensive search mechanism for numerical optimization

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Journal of Systems Engineering and Electronics 2015年第3期26卷 603-617页

作者： Mudong Li Hui Zhao Xingwei Weng Hanqiao Huang Department of Aeronautics and Astronautics Engineering Air Force Engineering University

The artificial bee colony （ABC） algorithm is a sim- ple and effective global optimization algorithm which has been successfully applied in practical optimization problems of various fields. However, the algorithm is still insufficient in balancing ex- ploration and exploitation. To solve this problem, we put forward an improved algorithm with a comprehensive search mechanism. The search mechanism contains three main strategies. Firstly, the heuristic Gaussian search strategy composed of three different search equations is proposed for the employed bees, which fully utilizes and balances the exploration and exploitation of the three different search equations by introducing the selectivity probability P,. Secondly, in order to improve the search accuracy, we propose the Gbest-guided neighborhood search strategy for onlooker bees to improve the exploitation performance of ABC. Thirdly, the self- adaptive population perturbation strategy for the current colony is used by random perturbation or Gaussian perturbation to en- hance the diversity of the population. In addition, to improve the quality of the initial population, we introduce the chaotic opposition- based learning method for initialization. The experimental results and Wilcoxon signed ranks test based on 27 benchmark func- tions show that the proposed algorithm, especially for solving high dimensional and complex function optimization problems, has a higher convergence speed and search precision than ABC and three other current ABC-based algorithms.

关键词： artificial bee colony (ABC) function optimization,search strategy population initialization Wilcoxon signed ranks test.

Vibration Fatigue Probabilistic Life Prediction Model and Method for Blade

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第3期35卷 494-506页

作者： Lou Guokang Wen Weidong Wu Fuxian Zhang Hongjian College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics

Vibration fatigue is one of the main failure modes of *** vibration fatigue life of blade is scattered caused by manufacture error,material property dispersion and external excitation randomness.A new vibration fatigue probabilistic life prediction model(VFPLPM)and a prediction method are proposed in this ***,as one-dimensional volumetric method(ODVM)only considers the principle calculation direction,a three-dimensional space vector volumetric method(TSVVM)is proposed to improve fatigue life prediction accuracy for actual threedimensional engineering ***,based on the two volumetric methods(ODVM and TSVVM),the material C-P-S-N fatigue curve model(CFCM)and the maximum entropy quantile function model(MEQFM),VFPLPM is established to predict the vibration fatigue probabilistic life of *** VFPLPM is combined with maximum stress method(MSM),ODVM and TSVVM to estimate vibration fatigue probabilistic life of blade simulator by finite element simulation,and is verified by vibration fatigue *** results show that all of the three methods can predict the vibration fatigue probabilistic life of blade simulator *** &TSVVM method has the highest computational accuracy for considering stress gradient effect not only in the principle calculation direction but also in other space vector directions.

关键词： vibration fatigue probabilistic life prediction C-P-S-N fatigue curve volumetric method maximum entropy quantile function