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Machining of SiC ceramic matrix composites:A review

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Chinese Journal of Aeronautics 2021年第4期34卷 540-567页

作者： Qinglong AN Jie chen Weiwei ming ming chen State Key Laboratory of Mechanical System and Vibration School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Continuous fiber reinforced SiC ceramic matrix composites(FRCMCs-SiC)are currently the preferred material for hot section components,safety–critical components and braking components(in the aerospace,energy,transportation)with high value,and have triggered the demand for ***,the high brittleness,anisotropy,and heterogeneity of materials bring great challenges to machining,due to high mechanical and thermal loads,severe tool wear,and poor machining *** the increasing demand of FRCMCs-SiC parts,high-quality and high-efficient machining has become a hot *** review paper provides a detailed literature survey on the machining of *** material removal mechanism,defect form,and interfacial mechanical properties of FRCMCs-SiC were *** machining processes of FRCMCs-SiC were introduced,and their respective advantages and disadvantages were *** the low machinability(high hardness,high brittleness,anisotropy,and heterogeneity)of FRCMCs-SiC,preliminary experiments have proved that ultrasonic-assisted machining and laser-assisted machining have shown unique advantages in reducing force and tool wear,improving machining quality and machining *** machined surface integrity was discussed,the influence of process parameters on the machined surface quality was analyzed,and the machining defects of FRCMCs-SiC were *** for FRCMCs-SiC,the existing quantitative evaluation of the machined surface integrity was weak and unsystematic.

关键词： Ceramic matrix composites Machining Material removal mechanisms Quality Surface integrity

Torsion Fields Generated by the Quantum Effects of Macro-bodies

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Research in Astronomy and Astrophysics 2022年第12期22卷 335-343页

作者： Da-ming chen National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China

We generalize Einstein's General Relativity(GR)by assuming that all matter(including macro-objects)has quantum *** appropriate theory to fulfill this task is Gauge Theory Gravity(GTG)developed by the Cambridge *** is a“spin-torsion”theory,according to which,gravitational effects are described by a pair of gauge fields defined over a flat Minkowski background *** matter content is completely described by the Dirac spinor field,and the quantum effects of matter are identified as the spin tensor derived from the spinor *** existence of the spin of matter results in the torsion field defined over *** field plays the role of Bohmian quantum potential which turns out to be a kind of repulsive force as opposed to the gravitational potential which is *** equivalence principle remains and essential in this theory so that GR is relegated to a locally approximate theory wherein the quantum effects(torsion)are *** a toy model,we assume that the macro matter content can be described by the covariant Dirac equation and apply this theory to the simplest radially symmetric and static gravitational ***,by virtue of the cosmological principle,we are led to a static universe model in which the Hubble redshifts arise from the torsion fields.

关键词： cosmology:theory (cosmology:)dark matter (cosmology:)dark energy

Magnetic reconnection acceleration of astrophysical jets for different jet geometries

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Research in Astronomy and Astrophysics 2015年第4期15卷 475-482页

作者： A-ming chen Li-ming Rui College of Physical Science and Technology Central China Normal University

The acceleration mechanisms of relativistic jets are of great importance for understanding various astrophysical phenomena such as gamma-ray bursts, active galactic nuclei and microquasars. One of the most popular scenarios is that the jets are initially Poynting-flux dominated and succumb to magnetohydrodynamic instability leading to magnetic reconnections. We suggest that the reconnection timescale and efficiency could strongly depend on the geometry of the jet, which determines the length scale on which the orientations of the field lines change. In contrast to a usually- assumed conical jet, the acceleration of a collimated jet can be found to be more rapid and efficient （i.e. a much more highly saturated Lorentz factor can be reached） while the jets with lateral expansion show the opposite behavior. The shape of the jet could be formed due to the lateral squeezing on the jet by the stellar envelope of a collapsing massive star or the interaction of the jet with stellar winds.

关键词： gamma rays: bursts -- galaxies: jets -- MHD -- instabilities

Shock-produced akimotoite in the Suizhou L6 chondrite

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Science China Earth Sciences 2015年第6期58卷 876-880页

作者： chen ming XIE XianDe State Key Laboratory of Isotope Geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences Key Laboratory of Mineralogy and Metallogeny Guangzhou Institute of Geochemistry Chinese Academy of Sciences

Shock-produced akimotoite was identified in the Suizhou chondritic meteorite, which occurs in two kinds of occurrence. The first is the irregular layers of akimotoite up to 4 ?m in thickness occurring in fractures and cracks of low-Ca pyroxene enclosed in the shock veins. The second is the zonal polycrystalline aggregates of akimotoite in shocked pyroxene grains close to the shock vein, where akimotoite occurs in a zonal area in between pyroxene and Mg Si O3-glass as irregular small clumps up to 5 ?m in size. This investigation suggests a solid-state transformation mechanism of pyroxene to akimotoite, and that akimotoite should have nucleated and grew in the area with abundant defects caused by shock deformation because the defect significantly enhances the solid-state reactivity and the kinetics of nucleation of high-pressure phase. The spatial relationship among the composed grains of pyroxene, akimotoite and Mg Si O3-glass(possibly vitrified perovskite) demonstrates a temperature gradient from the vein wall to the unmelted chondritic meteorite.

关键词： pyroxene akimotoite perovskite shock vein Suizhou meteorite

Characterization of Ser73 in Arabidopsis thaliana Glutathione S-transferase zeta class

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Journal of Genetics and Genomics 2008年第8期35卷 507-512页

作者： Sudan Tao Xiwen chen Jia Liu ming ming Namsu Chong Defu chen Laboratory of Molecular Genetics College of Life Sciences Nankai University Tianjin 300071 China

Glutathione S-transferases （GSTs） are ubiquitous detoxifying superfamily enzymes. The zeta class GST from Arabidopsis thaliana （AtGSTZ） can efficiently degrade dichloroacetic acid （DCA）, which is a common carcinogenic contaminant in drinking water. Ser73 in AtGSTZ is a conserved residue at Glutathione binding site （G-site）. Compared with the equivalent residues in other GSTs, the catalytic and structural properties of Ser73 were poorly investigated. In this article, site-saturation mutagenesis was performed to characterize the detailed role of Ser73. The DCA dechlorinating （DCA-DC） activity showed that most of the mutants had less than 3% of the wild-type activity, except S73T and S73A showing 43.48% and 21.62% of the wild-type activity, respectively, indicating that position 73 in AtGSTZ showed low mutational substitutability. Kinetic experiments revealed that mutants S73T, S73A, and S73G showed low binding affinity and catalytic efficiency toward DCA, 1.8-, 3.1-, and 10.7- fold increases in KmDcA values and 4.0-, 9.6-, and 34.1- fold decreases in Kcat- DCA/KmDCA values, respectively, compared to the wild type. Thermostability and refolding experiments showed that the wild type mainmined more thermostability and recovered activity. These results demonstrated the important role of Ser73 in catalytic activity and structural stability of the enzyme. Such properties of Ser73 could be particularly crucial to the molecular evolution of AtGSTZ and might, therefore, help explain why Ser73 is conserved in all GSTs. This conclusion might provide insights into the directed evolution of the DCA-DC activity of AtGSTZ.

关键词： Set73 thermostability refolding ability site-saturation mutagenesis ArGSTZ

Multi-stage Dynamic Post-disaster Recovery Strategy for Distribution Networks Considering Integrated Energy and Transportation Networks

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CSEE Journal of Power and Energy Systems 2021年第2期7卷 408-420页

作者： Xinyi Jiang Jian chen ming chen Zhen Wei Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education Shandong UniversityJinan 250061China State Grid Qingdao Power Supply Company Qingdao 266002China

To improve the resilience of distribution networks(DNs),a multi-stage dynamic recovery strategy is proposed in this paper,which is designed for post-disaster DN considering an integrated energy system(IES)and transportation network(TN).First,the emergency response quickly increases the output of gas turbines(GTs)in the natural gas network(NGN),and responsively reconfigures the DN in microgrids,to maximize the amount of loads to be *** single-commodity flow model is adopted to construct spanning tree ***,in the second stage of energy storage recovery,mobile energy storage systems(MESSs)are deployed to cover the shortages of power demands,i.e.,to further restore the loads after evaluating the load recovery *** Floyd algorithm based dynamic traffic assignment(DTA)is selected to obtain the optimal path of the *** the third stage,the outputs of various post-disaster recovery measures are adjusted to achieve an economically optimized *** studies demonstrate the effectiveness of the proposed dynamic post-disaster recovery strategy.

关键词： Dynamic post-disaster recovery dynamic transportation network integrated energy system resilience distribution

Feasibility study of creep feed grinding of 300M steel with zirconium corundum wheel

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Chinese Journal of Aeronautics 2022年第3期35卷 565-578页

作者： Jiaqiang DANG Heng ZANG Qinglong AN Weiwei ming ming chen School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Mechanical Systems and Vibration Shanghai Jiao Tong UniversityShanghai 200240China

The ultrahigh strength 300M steel has been commonly used in the manufacture of aircraft landing gear and rotor shaft parts due to its excellent mechanical *** feed grinding is one of the essential operations during the whole component manufacturing *** this work,the feasibility of creep feed grinding of 300M steel by using the hard zirconium corundum wheel was theoretically and experimentally evaluated.A variety of responses including grinding forces,temperature fields,specific grinding energy,surface integrity and chip modes were carefully ***,the mechanism of ground surface profile generation and the spatial frequency spectrum of the surface profile were tentatively *** was found that the wheel speed has a relative influence on the grinding forces and temperatures of which the work hardening effect dominates the material removal with lower wheel speed while the thermal softening becomes crucial as the wheel speed exceeds the critical value for the studied 300M ***,a scattered spatial frequency spectrum for the generated surface profile was noticed with lower wheel speed while the spectrum gathers towards the lower frequency values with higher amplitude as the wheel speed *** shearing chip and flowing chip dominates the main chip type,indicating the excellent abrasive sharpness during the grinding *** general,the used zirconium corundum wheel presents feasibility for the creep feed grinding of 300M steel because of the high material removal rate,absence of surface burn,low wheel wear and higher compressive residual stresses.

关键词： 300M steel Chip formation Creep feed grinding Surface morphology Zirconium corundum wheel

Design and Analysis of Hybrid Systems for Scooters

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Chinese Journal of Mechanical Engineering 2011年第5期24卷 752-759页

作者： chen I-ming LIU Tyng Department of Mechanical Engineering Taiwan University

Hybrid technology has been widely developed for various vehicles in recent ***,due to the limitation of size and space,it is difficult to apply the technology in the small two-wheeled vehicles,especially *** scooters,the hybrid system could be with small capacity,and must be simple and *** Purpose of this study is to analyze and develop the conceptual designs of fuel-electric hybrid systems especially for ***,the graph called ＂function power graph（FPG）＂ is defined,which transforms traditional mechanical schematic diagrams into simplified graphs,and makes the characteristics of hybrid systems can be identified *** on the FPG,a systematic method for synthesizing all possible arrangements of hybrid systems,then,is developed,and the hybrid system arrangements with one internal combustion engine（ICE）,one electric machine（M/G）,and some mechanical clutch units are all *** order to evaluate the applicability of these design concepts for Scooters,twelve system functions and three system complexities are defined,and this evaluation process can be automated numerically by using a computer program,which is Matlab in this *** the systematic design and analysis methods developed,the function capability and characteristics of current hybrid systems can be easily identified,and also,new and useful hybrid systems are found for future possible applications.

关键词： hybrid-system conceptual design automated synthesis scooter

Surface morphology characterization of unidirectional carbon fibre reinforced plastic machined by peripheral milling

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Chinese Journal of Aeronautics 2022年第2期35卷 361-375页

作者： Chongyan CAI Jiaqiang DANG Qinglong AN Weiwei ming ming chen School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China

This paper aims to characterise surface morphology and 3D roughness parameters of unidirectional carbon fibre reinforced plastic(UD-CFRP)milled at 0°,45°,90°,and 135°fibre orientation angles(FOAs).Side milling experiments are conducted on UD-CFRP *** damage forms and texture direction of milled surface are *** frequency of defects on CFRP surface is quantitatively determined using radially averaged 2D *** kinematicdynamic surface topography is reconstructed considering feed,runout and vibration,then the ideal roughness parameters,S_(a),S_(q),S_(sk),and S_(ku)are calculated and compared with the measured ones,finally the material factor-induced roughness components are *** show that CFRP surface has no regular feed *** frequency of fibre breakage or surface defects is greater than tooth passing *** sorted by their average S_(a)in descending order is135°>90°>45°>0°,where surface defects contribute 93.9%,77.1%,73.2%,72.2%of the total roughness respectively,which suggests that surface defects show a more important role than tool kinematics and vibration in formation of milled *** negative Skewness(Ssk<0)and high Kurtosis(S_(ku)=4.0–11.5)of milled surface signify porosity and the presence of many anomalous deep valleys in milled surface,respectively.

关键词： Carbon fibre reinforced plastic(CFRP) Surface characterization Surface morphology Surface roughness Surface texture