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Deformation behavior and microstructural evolution during hot compression of an a+b Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy

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International Journal of Minerals,Metallurgy and Materials 2011年第3期18卷 344-351页

作者： Gao-feng Liu Shang-zhou zhang Li-qing Chen jian-xun Qiu School of Environmental and Materials Engineering Yantai University Yantai 264005 China State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 China

The effect of processing parameters on the flow response and microstructural evolution of the a＋b titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si has been studied by conducting isothermal hot compressive tests at a strain rate of 0.01-10 s-1 at 860-1100°C. The true stress-true strain curves of the sample hot-compressed in the a＋b phase region exhibit a peak stress followed by continuous flow softening, whereas in the b region, the flow stress attains a steady-state regime. At a strain rate of 10 s-1, the alloy exhibits plastic flow insta-bilities. According to the kinetic rate equation, the apparent activation energies are estimated to be about 674-705 kJ/mol in the a＋b region and 308-335 kJ/mol in the b region, respectively. When deformed in the a＋b region, the globularization process of the a colony structure occurs, and a dynamic recrystallized microstructures are observed to show bimodal. Dynamic recrystallization can take place in the b region irrespective of starting deformed structures.

关键词： titanium alloys hot pressing deformation microstructural evolution activation energy

Critical Thrust Force Forecasting for Drilling Exit Delamination of Carbon Fibre Reinforced Plastics

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Transactions of Nanjing University of Aeronautics and Astronautics 2017年第4期34卷 372-379页

作者： zhang Lin Hu jian Tian Wei Liao Wenhe Bu Yin College of Mechanical and Electronical Engineering Nanjing University of Aeronautics and Astronautics

Exit delamination is excessive drilling thrust ***,it is necessary to investigate the critical thrust force which cause exit delamination when carbon fibre reinforced plastics(CRFP)is *** to the linear elastic fracture mechanics,the mechanics of composite material and the classical thin plate bending theory,a common theoretical model of the critical drilling thrust force for CFRP plates is *** with the experimental data of previous studies,the results show that the theoretical values agree well with the experimental *** model can be used to forecast the critical thrust force for the drilling-induced delamination of CFRP.

关键词： carbon fibre reinforced plastics standard twist drill drillings delamination critical thrust force

Leader-Follower UAV Formation Model Based on R5DOS-Intersection Model

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Computers, Materials & Continua 2021年第11期69卷 2493-2511页

作者： jian Li Weijian zhang Yating Hu Xiaoguang Li Zhun Wang College of Information Technology Jilin Agricultural UniversityChangchun130118China College of Electricity and Information Changchun Guanghua UniversityChangchun130033China Bioinformatics Research Center of Jilin Province Changchun130118China Department of Mathematical Sciences Delaware State University(DSU)Dover19901DE

This paper proposes a formation of multiple unmanned aerial vehicles(UAVs)based on the R5DOS(RCC-5 and orientation direction)intersection *** improving the R5DOS-intersection model,we evenly arranged 16 UAVs in 16 spatial *** with those of the rectangular formation model and the grid formation model,the communication costs,time costs,and energy costs of the R5DOS model formation were effectively *** the same time,the operation time of UAV formation was significantly *** leader-follower method can enhance the robustness of the UAV formation and ensure the integrity of communication during UAV formation ***,we conducted a simulation experiment on the model and found that the R5DOS model formation was stable and could maintain the desired *** randomly generated UAVs could quickly fly to the formation path in a short time,establish formation,and carry out *** the leader fails,the follower could travel to the original trajectory of the failed leader in a short time,replace the leader,and continue to communicate and improve the robustness of the *** sum up,the UAV formation based on the R5DOS model has the advantages of long operation time,strong endurance,low communication cost,and stable formation,which is of great significance for research on UAV formation.

关键词： Artificial intelligence RCC theory R5DOS intersection matrix UAV formation communication

Distributed cooperative guidance for multiple missiles with fixed and switching communication topologies

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Chinese Journal of Aeronautics 2017年第4期30卷 1570-1581页

作者： Qilun ZHAO Xiwang DONG Zixuan LIANG Chen BAI jian CHEN zhang REN Science and Technology on Aircraft Control Laboratory School of Automation Science and Electronic EngineeringBeihang University Beijing 100083 China School of Astronautics Beihang University Beijing 100083 China China Academy of Launch Vehcle Technology Beijing 100076 China College of Engineering China Agricultural University Beijing 100083 China

This study investigates cooperative guidance problems for multiple missiles with fixed and switching directed communication topologies. A two-step guidance strategy is proposed to realize the simultaneous attack. In the first step, a distributed cooperative guidance law is designed using local neighboring information for multiple missiles to achieve consensus on range-to-go and leading angle. The second step begins when the consensus of multiple missiles is realized. During the second step, multiple missiles disconnect from each other and hit the target using the proportional navigation guidance law. First, based on the local neighboring communications, a sufficient condition for multiple missiles to realize simultaneous attack with a fixed communication topology is presented, where the topology is only required to have a directed spanning tree. Then,the results are extended to the case of switching communication topologies. Finally, numerical simulations are provided to validate the theoretical results.

关键词： Consensus Cooperative guidance Directed topology Missile guidance Multiple missiles Switching communication topologies

High loading Pt nanoparticles on ordered mesoporous carbon sphere arrays for highly active methanol electro-oxidation

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Chinese Chemical Letters 2016年第6期27卷 832-836页

作者： Cheng-Wei zhang Lian-Bin Xu jian-Feng Chen State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical Technology Tianjin Key Laboratory of Materials Laminating Fabrication and Interface Control Technology Hebei University of Technology

Three-dimensionally（3D） ordered mesoporous carbon sphere arrays（OMCS） are explored to support high loading（60 wt%） Pt nanoparticles as electrocatalysts for the methanol oxidation reaction（MOR）.The OMCS has a unique hierarchical nanostructure with ordered large mesopores and macropores that can facilitate high dispersion of the Pt nanoparticles and fast mass transport during the reactions. The prepared Pt/OMCS exhibits uniformly dispersed Pt nanoparticles with an average size of- 2.0 nm on the mesoporous walls of the carbon spheres. The Pt/OMCS catalyst shows significantly enhanced specific electrochemically active surface area（ECSA）（73.5 m^2g^-1） and electrocatalytic activity（0.69 mA cm^-2）for the MOR compared with the commercial 60 wt% Pt/C catalyst.

关键词： Carbon Pt nanoparticles High loading Electrocatalyst Methanol oxidation reaction Fuel cell

Oxidative polymerization of hydroquinone using deoxycholic acid supramolecular template

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Science China Chemistry 2012年第5期55卷 830-835页

作者： zhang AiJuan HE jian GUAN Ying LI ZhanYong zhang Yongjun ZHU Julian X. Key Laboratory of Functional Polymer Materials Institute of Polymer ChemistryNankai UniversityTianjin 300071China Department of Chemistry Universitdde MontrealCP 6128Succ.Centre-villeMontrealQCH3C 3J7Canada

Polyhydroquinone (PHQ) is a redox-active polymer with quinone/hydroquinone redox active units in the main chain and may have potential applications as a mediator in biosensors and biofuel cells. By the oxidative polymerization of hydroquinone (HQ), PHQ can be easily synthesized, but the reaction lacks control over the structure of the product. Deoxycholic acid (DCA) was introduced as a supramolecular template to control the reaction. The reaction rate is 14 times of that in deionized water and twice of that in buffer. The DCA template increases not only the reaction rate, but also the molecular weight of the polymer obtained. The template effect of DCA was attributed to the supramolecular assemblies of DCA formed in the solution. Cyclic voltammetry study indicated the resulting PHQ was redox-active. While the supramolecular assemblies of DCA provided a template for the oxidative polymerization of HQ, the protons released as a by-product of the oxidative polymerization of HQ in turn enhanced the self-assembly of DCA. As a result, DCA microfibers form and separate out of the solution.

关键词： polyhydroquinone deoxycholic acid self-assembly oxidative polymerization

Laser cooling of CH molecule: Insights from ab initio study

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Chinese Physics B 2018年第10期27卷 276-282页

作者： Jie Cui jian-Gang Xu jian-Xia Qi Ge Dou Yun-Guang zhang School of Science Xi＇an University of Posts and TelecommunicationsXi＇an 710121China

The feasibility of laser cooling a CH molecule is investigated theoretically by employing the ab initio method. The potential energy curves for the five ∧-S states and eight Ω states of CH are determined by the multi-reference configuration interaction with the Davidson corrections（MRCI＋Q） level of theory. The results agree well with the available experimental data and other theoretical values. Also, the permanent dipole moments and transition dipole moments of the CH molecule are calculated at the multi-reference configuration interaction（MRCI） level. We find highly diagonally distributed FranckCondon factors（f00 = 0.9950 and 0.9998） and branching ratios（R00 = 0.983 and 0.993） for the A^2△→ X2Π and C^2∑^＋→X^2Π transitions. Moreover, the values of suitable radiative lifetime τ of the A2 A and C^2∑^＋ states are evaluated to be9.64×10^-7 s and 2.02×10^-7 s, respectively, for rapid laser cooling. A scheme for laser cooling the CH molecule is designed. In the proposed cooling scheme, three wavelengths for A^2△→X^2Π and C^2∑^＋→X^2Π transitions are used, and the main pump lasers are λ00=430.86 nm and 313.45 nm, respectively. The feasibility of laser cooling the CH molecules is demonstrated for each of these schemes, and this study offers a theoretical basis for experimental research into preparation of cold CH molecules.

关键词： spectroscopic constants transition diople moments Franck-Condon factors laser cooling

Enantioselective Alternating Copolymerization of Propylene with Carbon Monoxide Using Cationic Palladium-Chiral Diphosphine Catalyst

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Chinese Chemical Letters 2001年第6期12卷 519-522页

作者： jian Chao YUAN Yu Hua zhang Shi Jie LU State Key Laboratory for Oxo Synthesis and Selective Oxidation Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000

Enantioselective alternating copolymerization of carbon monoxide with propylene was carried out using palladium catalyst modified by 1,4-3,6-dianhydro-2,5-dideoxy-2,5-bis (diphenylphosphino)-L-iditol (DDPPI). The chiral diphosphine was proved to be effective at enantioselective copolymerization. Optical rotation, elemental analysis, H-1, C-13-NMR and IR spectra showed that the copolymer was optically active, isotactic, alternating poly(1,4-ketone) structure.

关键词： Palladium catalyst chiral ligand enantioselective alternating copolymerization isotactic copolymer optical activity

Spectral Properties and Photochromic Characteristics of Spiropyran Dyes

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Chemical Research in Chinese Universities 2006年第4期22卷 505-509页

作者： SHEN Kai-hua HAN jian-guo zhang Gang CHOI Dong-hoon The State Key Laboratory of Fine Chemicals Dalian University of Technology Dalian 116012 P. R. China The Key Laboratory of Cellulose and Lignocellulosics Chemistry Guangzhou Institute of Chemistry Chinese Academy of Sciences Guangzhou 510650 P. R. China Polymer and Fiber Material Engineering Kyunghee University Kyong Kido 449-701 Korea

A bis-benzospiropyran（BBSP） and nitro-substituted indoline spirobenzopyrans（SBP） were prepared by following a simple procedure. The reaction mechanism of synthesizing bis-benzospiropyran is discussed. A comparative analysis of the spectral and photochromic properties between SBP and BBSP was carried out with the aid of a PMMA film. The results indicate that chemical structures and UV irradiation played an important role in the spectral and photochromic properties of SBP and BBSP, which would readily affect λmax of the colored forms and the reversibility. The IR spectra and ^1H NMR spectra of these compounds are used to interpret the photochromic phenomena under different UV irradiation and determine the configurations of SBP and BBSP.

关键词： Photochromism Spiropyran UV radiation Protonation