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H_∞ fault estimation for a class of linear time-delay systems in finite frequency domain

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j.urnal of Systems Engineering and Electronics 2010年第5期21卷 835-841页

作者： Quanchao dong Maiying Zhong Steven x. Ding School of Control Science and Engineering Shandong University Jinan 250061 E R. China School of Instrumentation Science and Opto-electronics Engineering Beihang University Beijing 100191 P. R. China Institute for Automatic Control and Complex.Systems University of Duisburg-Essen Duisburg 47057 Germany

This paper deals with the problem of H∞ fault estimation for linear time-delay systems in finite frequency *** a generalized coordinate change is applied to the original system such that in the new coordinates all the time-delay terms are inj.cted by the system＇s input and *** an observer-based H∞ fault estimator with input and output inj.ctions is proposed for fault estimation with known frequency *** the aid of Generalized Kalman-Yakubovich-Popov lemma,sufficient conditions on the ex.stence of the H∞ fault estimator are derived and a solution to the observer gain matrices is obtained by solving a set of linear matrix.***,a numerical ex.mple is given to illustrate the effectiveness of the proposed method.

关键词： fault estimation time-delay generalized coordinate change generalized Kalman-Yakubovich-Popov lemma finite frequency domain.

Tunable near- to mid-infrared pump terahertz probe spectroscopy in reflection geometry

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Frontiers of physics 2017年第5期12卷 81-85页

作者： S. j. Zhang Z. x. Wang T. dong N. L. Wang International Center for Quantum Materials School of Physics Peking University Beijing 100871 China Collaborative Innovation Center of Quantum Matter Beijing 100871 China

Strong-field mid-infrared pump-terahertz （THz）probe spectroscopy has been proven as a powerful tool for light control of different orders in strongly correlated materials. We report the construction of an ultrafast broadband infrared pump-THz probe system in reflection geometry. A two-output optical parametric amplifier is used for generating mid-infrared pulses with GaSe as the nonlinear crystal. The setup is capable of pumping bulk materials at wavelengths ranging from 1.2 μm to 15 μm and beyond, and detecting the subtle, transient photoinduced changes in the reflected electric field of the THz probe at different temperatures. As a demonstration, we present 15 μm pump-THz probe measurements of a bulk EuSbTe3 single crystal. A 0.5% transient change in the reflected THz electric field can be clearly resolved. The widely tuned pumping energy could be used in mode-selective ex.itation ex.eriments and applied to many strongly correlated electron systems.

关键词： mid-infrared pump terahertz spectroscopy

Electron mass enhancement and magnetic phase separation near the Mott transition in double-layer ruthenates

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Frontiers of physics 2018年第4期13卷 159-165页

作者： j.n Peng x. M. Gu G. T. Zhou W. Wang j. Y. Liu Yu Wang Z. Q. Mao x. S. Wu Shuai dong School of Physics Southeast University Nanjing 211189 China Collaborative Innovation Center of Advanced Microstrucutres Lab of Solid State Microstructures School of Physics Nanjing University Nanjing 210093 China Department of Physics and Engineering Physics Tulane University New Orleans LA 70118 USA

We present a detailed investigation of the specific heat of Ca3（Ru1-x.x.2O7 （M = Ti, Fe, Mn） single crystals. Depending on the dopant and doping level, three distinct regions are present： a quasi- two-dimensional metallic state with antiferromagnetic （AFM） order formed by ferromagnetic bilayers （AFM-b）, a Mott insulating state with G-type AFM order （G-AFM）, and a localized state with a mix.d AFM-b and G-AFM phase. Our specific heat data provide deep insights into the Mort transitions induced by Ti and Mn doping. We observed not only an anomalous large mass enhancement, but also an additional term in the specific heat, i.e., C ∝ T2, in the localized region. The C ∝ T2 term is most likely due to long-wavelength ex.itations with both FM and AFM components. A decrease in the Debye temperature is observed in the G-type AFM region, indicating lattice softening associated with the Mott transition.

关键词： specific heat ruthenates Mort insulator phase separation

Corrosion Evolution of Reinforcing Steel in Concrete under Dry/Wet Cyclic Conditions Contaminated with Chloride

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j.urnal of Materials Science & Technology 2012年第10期28卷 905-912页

作者： j.Wei x.x.Fu j.H.dong W.Ke State Key Laboratory of Corrosion and Protection Institute of Metal ResearchChinese Academy of SciencesShenyang110016~China

The corrosion evolution of rebar in concrete was monitored by electrochemical impedance spectroscopy （EIS） under dry/wet alternated accelerated corrosion test. Four stages with different dynamic characteristics were observed during the corrosion evolution. They were passive stage, local corrosion controlled by the charge transfer step, accelerated corrosion controlled by the mass transfer step, and constant rate corrosion controlled by the mass transfer step through a barrier layer. x.ray diffraction （x.D） analysis showed that the corrosion product of rebar in mortar was composed of α-FeOOH, γ-FeOOH and Fe304. The corrosion mechanisms of all four stages were discussed and the corrosion reactions were proposed according to the corrosion product and corrosion evolution characteristics.

关键词： Rebar Concrete Electrochemical impedance spectroscopy (EIS) Corrosionevolution

A DUCTILE FRACTURE CRITERION BASED ON THREEDIMENSIONAL VOID MODEL

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Acta Metallurgica Sinica(English Letters) 2008年第3期21卷 227-234页

作者： j.K. Huang x.H. dong National Die ＆ Mould CAD Engineering Research Center Shanghai Jiaotong University Shanghai 200030China

A fracture criterion derived from a microscopic point of view is proposed and has proved to be effective in the analysis of uniax.al tension. On the one hand, a method of predicting a ductile fracture is proposed using a three-dimensional void model and the assumption of velocity discontinuity. The relationship between the void volume fraction and the critical strain to fracture, calculated with the help of the new model, shows the same tendency as that obtained from the modified Thomason model. On the other hand, the mechanical and metallographic analyses of the uniax.al tension ex.eriment are performed using four kinds of carbon steel. The relationship between the void volume fraction and the critical strain to fracture, calculated from the new model, agrees better with the result obtained from the ex.eriment, rather than that calculated by the modified Thomason model, which confirms the validity of the ductile fracture criterion based on the three-dimensional void model.

关键词： Fracture criterion Uniax.al tension Velocity discontinuity Mechanical and metallographic analyses

Fatigue Behavior of HDPE Composite Reinforced with Silane Modified TiO_2

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j.urnal of Materials Science & Technology 2011年第7期27卷 659-667页

作者： C.x. dong S.j. Zhu Mineo Mizuno Masami Hashimoto Department of Intelligent Mechanical Engineering Fukuoka Institute of Technology Fukuoka 811-0295 Japan Nanomaterials Laboratory Beihua University Jilin 132013 China j.pan Fine Ceramics Center Nagoya 456-8587 Japan

The composite of high density polyethylene reinforced with silane-modified TiO2 particles （silane-TiO2/HDPE） is a potential bone substitute biomaterial. The structure, bioactivity, and mechanical properties of silane-TiO2/HDPE are analogous to those of natural bone, correspondingly. In order to investigate the effect of silane connection and saline solution on fatigue behaviors, flex.ral fatigue tests with this composite were carried out in both air and saline solution. Saline solution was found to have different effect on fatigue life. In saline solution, the fatigue life could be improved at stress levels lower than 30 MPa, while the fatigue life could be reduced at stress levels higher than 30 MPa. After analyzing the fracture morphologies, different failure mechanisms were proposed, and the important role of silane connection in the composite during the fatigue process was discussed. Silane connection cannot only support the loading stress but also hinder the failure process under loading effectively. For dry specimens, no interfacial failure between the filler and matrix.was found. For wet specimens, it is inferred that the synergetic effect of saline solution and high concentrated stress at high stress level could easily destroy the silane connection, which accelerated the fracture process, whereas the synergetic effect of saline solution and silane connection at low stress level could promote the formation of more microcracks on sample surface, which hindered the final fracture.

关键词： Fatigue Composites Polymers Fracture Interfaces

Ex.ERIMENTAL INVESTIGATION AND THERMODYNAMIC CALCULATION ON PHASE PRECIPITATION OF INCONEL 740

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Acta Metallurgica Sinica(English Letters) 2006年第6期19卷 425-431页

作者： S.Q.Zhao Y.j.ang j.x.dong x.S.x.e Department of Physics Ningxia UniversityYinchuan 750021China Department of Materials Science The Northwest Second Nationalities InstituteYinchuan 750021China High Temperature Materials Research Laboratories University of Science and Technology BeijingBeijing 100083China

A novel nickel-based superalloy INCONEL 740 was under development for application in ultra-supercritical superheater tubers above 750℃. The precipitation behaviors of η phase and γ' particles of the alloy were investigated through ex.erimental study and phase computation. Ex.erimental results showed that η phase formed a Widmanst?tten pattern structure following long-term ex.osure at elevated temperatures and that the coarsening of γ' particle follows a cube rate law:r-3 ∝ t. Thermodynamic calculation results showed that Al and Ti had an important effect on the precipitation behavior of γ' andη phases. Two suggested novel modified alloys, wherein the Al and Ti contents were modified, were designed and melted for the ex.erimental study. The preliminary results indicated that the modified alloys ex.ibited higher structural stability following long-term ex.osure at 750℃ till 5000h.

关键词： superalloy INCONEL 740 precipitate thermodynamic calculation

STUDY OF DYNAMIC RECRYSTALLIZATION OF LOW CARBON STEEL IN THIN SLAB CONTINUOUS ROLLING PROCESS

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Acta Metallurgica Sinica(English Letters) 2006年第4期19卷 265-270页

作者： x.K. Liang x.j. Sun Q.Y. Liu H. dong State Key Laboratory of Advanced Steel Processes and Products Central Iron and Steel Research Institute Beijing 100081 China

Combined with the technological characteristics of thin slab continuous rolling process （TSCR）, dynamic recrystallization of an ex.remely coarse austenite of low carbon steel is studied by Thermecmaster-Z hot simulator. By the analysis of true stress-strain curves and the observation of microstructures at different deformation stages, the critical stress and critical strain are determined under different deformation conditions. The effect of Z parameter on dynamic recrystallization of coarse austenite is studied. The microstructure evolution in real production is also discussed.

关键词： TSCR (thin slab continuous rolling process) coarse austenite dynamic recrystallization

PHASE TRANSFORMATION AND CHARACTERISTICS IN FRECKLE AREAS FOR INCONEL 625 SUPERALLOY

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Acta Metallurgica Sinica(English Letters) 2005年第1期18卷 47-54页

作者： j.x.dong M.C.Zhang Y.P.Zeng x.S.x.e UniversityofScienceandTechnologyBeij.ng Beijing100083China

The freckle formation and their phase characterizatics in freckle areas were investigated by means of microstructure analysis approaches and a thermodynamic equilibrium phase calculation method in an Inconel 625 allay. These results show that in freckle areas a large number of M6C, MC, Laves and δ phases precipitate in grain boundaries even within grain due to the enrichment and segregation of Mo and Nb during solidification, which results in almost of these freckle areas covered by these complex.precipitated phases and induces small grains in freckle areas. Equilibrium phase and liquid segregation calculation can give a reasonable interpretation of the freckle feature for this alloy.

关键词： freckle superalloy Inconel 625 thermodynamic calculation