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A hybrid multi-degree-of-freedom vibration isolation platform for spacecrafts by the linear active disturbance rejection control

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Applied Mathematics and Mechanics(English Edition) 2020年第5期41卷 805-818页

作者： Weichao ChI s.J.MA J.q.sUN College of science Northeastern UniversityShenyang 100819China Key Laboratory of Ministry of Education on safe Mining of Deep Metal Mines Northeastern UniversityShenyang 100819China Department of Mechanical Engineering School of EngineeringUniversity of CaliforniaMercedCA 95343U.S.A.

The hybrid vibration isolation, which takes advantages of both the passive and active approaches, has been an important solution for space missions. The objective of this paper is to design a vibration isolation platform for payloads on spacecrafts with the robust, wide bandwidth, and multi-degree-of-freedom(MDOF). The proposed solution is based on a parallel mechanism with six voice-coil motors(VCMs) as the actuators. The linear active disturbance resistance control(LADRC) algorithm is used for the active control. Numerical simulation results show that the vibration isolation platform performs effectively over a wide bandwidth, and the resonance introduced by the passive isolation is eliminated. The system robustness to the uncertainties of the structure is also verified by simulation.

关键词： hybrid vibration isolation stewart platform linear active disturbance rejection control(LADRC) stability robustness

Kinetic studies of Electrochemical Oxidation of 1,3-Benzenedithiol

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Chemical Research in Chinese Universities 1993年第3期9卷 231-239页

作者： h.s.Lee X.q.Yang J.McBreen T.A.skotheim Brookhaven National Laboratory Upton NY 11973 U.S.A. Brookhaven National Laboratory Upton NY 11973 U.S.A. Brookhaven National Laboratory Upton NY 11973 U.S.A. Moltech Corporation Stony Brook NY 11790-3350 U.S.A.

The electrochemical oxidation of 1, 3-benzenedithiol was investigated in a 0. 100 mol/L tetrabutylammonium perchlorate/acetonitrile electrolyte. The electrochemical techniques used were potential sweep, bulk electrolysis, rotating disc and the potential step method. The combination of the techniques yielded the number of electrons transferred per molecule, the reaction order, the transfer coefficient, the diffusion coefficient and concentration of dithiol anions, the standard heterogeneous rate constant as well as the formal potential and equilibrium constant of the preceeding dissociation reaction. This paper also illustrates the methods for studying the electrode kinetics of reactions which (a) involve a chemical reaction preceeding the electron-transfer process, (b) have insoluble polymer products, and (c) are totally irreversible.

关键词： Electrochemical oxidation 1,3-Benzenedithiol Electrode kinetics Organ-ic disulfide

Full-band error control and crack-free surface fabrication techniques for ultra-precision fly cutting of large-aperture KDP crystals

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Frontiers of Mechanical Engineering 2017年第2期12卷 193-202页

作者： F. h. ZhANG s. F. WANG C. h. AN J. WANG q. XU Department of Mechanical Engineering Harbin Institute of TechnologyHarbin 150001 China Chengdu Fine Optical Engineering Research Center Chengdu 610041China

Large-aperture potassium dihydrogen phos- phate （KDP） crystals are widely used in the laser path of inertial confinement fusion （ICF） systems. The most common method of manufacturing half-meter KDP crystals is ultra-precision fly cutting. When processing KDP crystals by ultra-precision fly cutting, the dynamic characteristics of the fly cutting machine and fluctuations in the fly cutting environment are translated into surface errors at different spatial frequency bands. These machin- ing errors should be suppressed effectively to guarantee that KDP crystals meet the full-band machining accuracy specified in the evaluation index. In this study, the anisotropic machinability of KDP crystals and the causes of typical surface errors in ultra-precision fly cutting of the material are investigated. The structures of the fly cutting machine and existing processing parameters are optimized to improve the machined surface quality. The findings are theoretically and practically important in the development of high-energy laser systems in China.

关键词： ultra-precision fly cutting large-aperture KDP crystals spatial frequency processing error

Contamination by Organochlorine Pesticides in the Estuaries of southeast China

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Chemical Research in Chinese Universities 2002年第2期18卷 153-160页

作者： Z.L.Zhang h.s.hong J.L.Zhou M.h.Dai K.Maskaouib W.q.Chen Department of Environmental science and Engineering Tsinghua POPs Research CentreTsinghua UniversityBeijing 100084China Key Laboratory of Marine Environmental science of Ministry of Education Environmental Science Research CentreXiamen Universi-tyXiamen 361005China school of Chemistry Physics and Environmental ScienceUniversity of SussexFalmerBrighton BN19QJUK

Persistent organic pollutants(POPs) such as organochlorine pesticides are of global concern due to their widespread occurrence and persistence. This paper reports recent research studying the distribution and fate of organochlorine pesticides in the Jiulong River, the Minjiang River and the Pearl River estuaries in southeast China. Eighteen organochlorine pesticides were extracted from water, pore water and sediment samples, followed by analysis by GC ECD. The results showed that the contamination levels were similar in these three estuaries. The levels of the total organochlorine pesticides in porewater were significantly higher than those in surface water, due to the high affinity of these hydrophobic compounds for sediment phase. Among the hexachlorocyclohexane(hCh) compounds, β hCh was found to be the most important isomer. The analysis of 1,1,1 trichloro 2,2 bis chlorophenyl ethane(DDT) and its metabolites showed that 1,1 dichloro 2[ o chlorophenyl] 2[ p chlorophenyl] ethylene(DDE) was dominant in the group.

关键词： Organochlorine insecticides DDT Lindane Jiulong River Estuary Minjiang River Estuary Pearl River Estuary Water sediment

Effect of Icosahedral Phase on Crystallographic Texture and Mechanical Anisotropy of Mg–4%Li Based Alloys

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Journal of Materials science & Technology 2017年第5期33卷 475-480页

作者： C.q.Li D.K.Xu s.Yu L.Y.sheng E.h.han school of Materials science and Engineering Northeastern University CAs Key Laboratory of Nuclear Materials and safety Assessment Institute of Metal Research Chinese Academy of Sciences school of Materials science and Engineering Shenyang Aerospace University shenzhen Institute Peking University Shenzhen Key Lab Human Tissue Regenerate & Repair

Through investigating and comparing the microstructure and mechanical properties of the as-extruded Mg alloys Mg-4%Li and Mg-4%Li-6%Zn-l.2%Y （in wt%）, it demonstrates that although the formation of I-phase （Mg3Zn6Y, icosahedral structure） could weaken the crystallographic texture and improve the me- chanical strength, the mechanical anisotropy in terms of strength remains in Mg-4%Li-6%Zn-1.2%Y alloy. Failure analysis indicates that for the Mg-4%Li alloy, the fracture surfaces of the tensile samples tested along transverse direction （TD） contain a large number of plastic dimples, whereas the fracture surface exhibits quasi-cleavage characteristic when tensile samples were tested along extrusion direction （ED）. For the Mg-4%Li-6%Zn-I.2%Y alloy, typical ductile fracture surfaces can be observed in both ＂TD＂ and ＂ED＂ samples. Moreover, due to the zonal distribution of broken l-phase particles, the fracture surface of ＂TD＂ samples is characterized by the typical ＂woody fracture＂.

关键词： Mg-Li alloy Texture Mechanical anisotropy Fracture

Adiabatic shear instability in a titanium alloy:Extreme deformation-induced phase transformation,nanotwinning,and grain refinement

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Journal of Materials science & Technology 2023年第19期150卷 104-113页

作者： X.R.Guan q.Chen s.J.qu G.J.Cao h.Wang A.h.Feng D.L.Chen school of Materials science and Engineering Tongji UniversityShanghai 201804China southwest Technology and Engineering Research Institute Chongqing 400039China shanghai Key Laboratory of D&A for Metal-Functional Materials School of Materials Science&EngineeringTongji UniversityShanghai 201804China Key Laboratory for Light-weight Materials Nanjing Tech UniversityNanjing 210009China Interdisciplinary Center for Additive Manufacturing School of Materials and ChemistryUniversity of Shanghai for Science and TechnologyShanghai 2000093China Department of Mechanical and Industrial Engineering Toronto Metropolitan University(formerly Ryerson University)TorontoON M5B 2K3Canada

Increasingly harsh service conditions place higher requirements for the high strain-rate performance of titanium *** shear band(AsB),a phenomenon prone to dynamic loading,is often accom-panied by catastrophic ***,it is unclear how the internal nanostructures are related to shear *** we report detailed microstructural evolution in the AsB of a titanium alloy via in-depth focused ion beam(FIB),transmission Kikuchi diffraction(TKD),and high-resolution transmission electron microscope(hRTEM)analyses,with the deformation instability phenomenon discussed from the energy *** AsB interior undergoes multifaceted changes,namely deformation-induced beta-to-alpha transformation and deformation-induced martensitic transformation to form substantially refined and heterogeneous ***,two types of extremely fine twins are identified to occur within both nano-sized martensite and alpha *** critical plastic work representing the onset of adiabatic shear instability and dynamic equilibrium is observed to be constant for a specific structure in the same deformation *** energy analysis could be extended to other materials subjected to high strain-rate dynamic deformation.

关键词： Adiabatic shear instability Deformation-induced phase transformation Deformation-induced nanotwinning Dynamic recovery Energy analysis

Mechanical Properties of a Low-thermal-expansion Aluminum/silicon Composite Produced by Powder Metallurgy

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Journal of Materials science & Technology 2014年第4期30卷 417-422页

作者： Y.q.Liu s.h.Wei J.Z.Fan Z.L.Ma T.Zuo National Engineering & Technology Research Center for Nonferrous Metal Matrix Composites Beijing General Research Institute for Nonferrous Metals

AI matrix composite containing high volume fraction silicon has been promising candidate for lightweight and low-thermal-expansion components. Whereas, optimization of its mechanical properties still is an open challenge. In this article, a flexile powder metallurgy processing was used to produce a fully dense AI-4.0Cu （wt%） alloy composite reinforced with 65 vol.% si particles. In this composite, si particles were homogenously distributed, and the particle size was refined to the range of 3-15 μm. Tensile and flexural strength of the composite were 282 and 455 MPa, respectively, about 100% and 50% higher than the best properties reported in literature. The measured fracture toughness of the composite was 4.90 MPa m1/2. The improved strength of 65%si/AI was attributed to the optimized particle characteristics and matrix properties. This investigation is expected to provide a primary understanding of the mechanical behaviors of si/AI composites, and also promote the structural applications of this low-thermal-expansion material.

关键词： Aluminum matrix composite Powder metallurgy Mechanical properties Coefficient of thermal expansion Fracture

synergistic O^(2-)/Li^(+) Dual Ion Transportation at Atomic scale

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Research 2019年第1期2019卷 1260-1267页

作者： F.q.Meng q.h.Zhang A.Gao X.Z.Liu J.N.Zhang s.Y.Peng X.Lu L.Gu h.Li Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China school of Materials Sun Yat-Sen UniversityGuangzhou 510275China College of Materials science and Engineering Jiangxi University of Science and TechnologyJiangxi 341000China songshan Lake Materials Laboratory DongguanGuangdong 523808China school of Physical sciences University of Chinese Academy of SciencesBeijing 100049China

Te ion migration during electrochemical process is a fundamental scientifc issue for phase transition behavior and of technical importance for various functional devices,where cations or anions are active under electrical *** only one type of functional ion,O^(2-)or Li^(+),is activated due to their diferent migration energy barriers,cooperated by the valence change of other immobile ions in the host lattice matrix,e.g.,Co^(2+)/Co^(3+)and Mn^(3+)/Mn4+redox couples,owing to the charge *** we select spinel Li4Ti5O12 as anode and construct an all-solid-state battery under a transmission electron microscope;a synergistic transportation of O^(2-)and Li^(+)driven by an electrical bias was directly observed at the atomic scale.A small amount of oxygen anions was extracted frstly as a result of its lowest vacancy formation energy under 2.2 V,leading to the vertical displacement of *** to 2.7 V,an ordered phase with both Li-and O-defciency *** Li^(+)and O^(2-)ions are simultaneously extracted out from the[LiO_(4)]tetrahedra due to the electroneutrality *** migration paths of O and Li have been proposed and verifed by frst-principles *** results reveal a brand new synergistic ion migration manner and may provide up-to-date insights on the transportation process of lithium ion conductors.

关键词： synergistic battery migration

Plastic strain Energy Model for Rock salt Under Fatigue Loading

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Acta Mechanica solida sinica 2018年第3期31卷 322-331页

作者： M.M.he N.Li B.q.huang C.h.Zhu Y.s.Chen Institute of Geotechnieal Engineering Xi'an University of TechnologyXi'an 710048China state Key Laboratory of Eco-hydraulics in Northwest Arid Region Xi'an University of TechnologyXi'an 710048China College of Information Engineering and Automation Kunming University of Science and TechnologyKunming 650500China shaanxi Key Laboratory of Loess Mechanics and Engineering Xi'an University of TechnologyXi'an 710048China

The fatigue test for rock salt is conducted to investigate the effects of stress ampli- tude, loading frequency and loading rate on the plastic strain energy, from which the evaluation rule of the plastic strain energy is analyzed, which is divided into three stages： cyclic hardening, saturation and cyclic softening. The total accumulated plastic strain energy only depends on the mechanical behavior of rock salt, but is immune to the loading conditions. A novel model for fatigue life prediction is proposed based on the invariance of the total plastic dissipation energy and the stability of the plastic energy per cycle.

关键词： Rock salt Fatigue life Plastic energy