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A Crystal-Plasticity Cyclic Constitutive Model for the Ratchetting of Polycrystalline Material Considering Dislocation Substructures

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Acta Mechanica Solida Sinica 2020年第2期33卷 268-280页

作者： Xuehong ren Shaopu Yang Guilin wen wenjie Zhao State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangsha 410082China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China

A crystal-plasticity cyclic constitutive model of polycrystalline material considering intra-granular heterogeneous dislocation substructures,in terms of three dislocation categories:mobile dislocations,immobile dislocations in the cell interiors and in the cell walls,is proposed based on the existing microscopic and macroscopic experimental *** multiplication,annihilation,rearrangement and immobilization of dislocations on each slip system are taken as the basic evolutionary mechanism of the three dislocation categories,and the cross-slip of screw dislocations is viewed as the dynamic recovery mechanism at room *** slip resistance associated with the isotropic hardening rule results from the interactions of dislocations on the slip ***,a modified nonlinear kinematic hardening rule and a rate-dependent flow rule at the slip system level are employed to improve the predictive capability of the model for ratchetting *** predictive ability of the developed model to uniaxial and mul-tiaxial ratchetting in macroscopic scale is verified by comparing with the experimental results of polycrystalline 316L stainless *** ratchetting in intra-granular scale which is obviously dependent on the crystallographic orientation and stress levels can be reasonably predicted by the proposed model.

关键词： Ratchetting Dislocation substructures Crystal plasticity Polycrystalline materials Constitutive model

Surface Photocatalysis-TPD Spectrometer for Photochemical Kinetics

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Chinese Journal of Chemical Physics 2012年第5期25卷 507-512,I0003页

作者： Ze-feng ren qing Guo Chen-biao Xu wen-shao Yang Chun-lei Xiao Dong-xu Dai Xue-ming Yang State Key Laboratory of Molecular Reaction Dynamics Dalian Institute of Chemical PhysicsDalian115023China School of Physics and Optoelectronic Technology Dalian University of TechnologyDalian 116024China

A surface photocatalysis-TPD apparatus devoted to studying kinetics and mechanism of pho- tocatalytic processes with various signal crystal surfaces has been constructed. Extremely high vacuum （-0.2 nPa） in the ionization region is obtained by using multiple ultrahigh vacuum pumps. Compared with similar instruments built previously by others~ the H2, CH4 background in the ionization region can be reduced by about two orders of magnitude, and other residual gases in the ionization region can be reduced by about an order of magnitude. Therefore, the signal-to-noise ratio for the temperature programmed desorption （TPD） and time of flight （TOF） spectra is substantially enhanced, making experimental studies of pho- tocatalytic processes on surfaces much easier. In this work, we describe the new apparatus in detail and present some preliminary studies on the photo-induced oxygen vacancy defects on TiO2（110） at 266 nm by using the TPD and TOF methods. Preliminary results suggest that the apparatus is a powerful tool for studying kinetics and mechanism of photochemical processes.

关键词： Temperature programmed desorption Time of flight spectrum Surface pho-tochemical kinetics

Multi-aperture seeing profiler with multiple guide stars

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Research in Astronomy and Astrophysics 2019年第4期19卷 53-62页

作者： Feng Yang Gang Zhao De-qing ren National Astronomical Observatories/Nanjing Institute of Astronomical Optics & Technology Chinese Academy of Sciences CAS Key Laboratory of Astronomical Optics & Technology Nanjing Institute of Astronomical Optics & Technology University of Chinese Academy of Sciences Physics & Astronomy Department California State University Northridge

The daytime atmospheric turbulence profile is crucial for the design of both optical systems and the control algorithm of a solar Multi-Conjugate Adaptive Optics(MCAO) system. The Multi-Aperture Seeing Profiler(MASP) is a portable instrument which can measure the daytime turbulence profile up to^30 km. It consists of two portable small telescopes that can deliver performance similar to a SolarDifferential Image Motion Monitor +(S-DIMM+) on a 1.0 m solar telescope. In the original design of MASP, only two guide stars are used to retrieve the turbulence profile. In this paper, we studied the usage of multiple guide stars in MASP using numerical simulation, and found that there are three main ***, the precision of the turbulence profile can be increased, especially at a height of about 15 km, which is important for characterizing turbulence at the tropopause. Secondly, the equivalent diameter of MASP can be increased up to 30%, which will reduce the cost and weight of the instruments. Thirdly, the vertical resolution of the turbulence profile near the ground increases with the help of multiple guide stars.

关键词： atmospheric effects site testing methods:numerical

Comparative study on flow and heat transfer characteristics of sinusoidal and zigzag channel printed circuit heat exchangers

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Science China(Technological Sciences) 2020年第4期63卷 655-667页

作者： wen Zhe-Xi LV Yi-Gao LI qing School of Energy Science and EngineeringCentral South UniversityChangsha 410083China

Printed circuit heat exchangers(PCHEs)are promising candidates for recuperators in supercritical CO2 Brayton cycles.A comparative study is given in this paper on the flow and heat transfer characteristics of PCHEs with sinusoidal and zigzag *** mass flow rates of 0.6–1.8 kg/h and the bend angles of 15°–30°,the thermal-hydraulic performance of the PCHEs is *** show that the sinusoidal channel is superior to the zigzag channel in its comprehensive *** bend angles result in greater reductions in pressure drop if sinusoidal channels are used instead of zigzag channels and a maximum of 48.4%reduction can be obtained in the considered working ***,the inlet sections should be carefully optimized since these sections account for up to 31%and 17%of the total pressure drop in the sinusoidal and zigzag channels,*** corner shape of the zigzag channel can be specially designed to further reduce the pressure *** nonuniform density and heat flux distributions in both channels are found to be related to the periodic changes of flow directions and the centrifugal forces should not be ignored when optimizing the sinusoidal and zigzag channels.

关键词： printed circuit heat exchanger supercritical CO2 thermal-hydraulic performance sinusoidal channel numerical simulation

Numerical analysis of modal tomography for solar multi-conjugate adaptive optics

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Research in Astronomy and Astrophysics 2012年第4期12卷 465-471页

作者： Bing Dong De-qing ren Xi Zhang Physics ＆ Astronomy Department California State University Northridge CA 91330-8268 USA National Astronomical Observatories/Nanjing Institute of Astronomical Optics ＆ Technology Chinese Academy of Sciences Nanjing 210042 China

Multi-conjugate adaptive optics （MCAO） can considerably extend the cor- rected field of view with respect to classical adaptive optics, which will benefit solar observation in many aspects. In solar MCAO, the Sun structure is utilized to provide multiple guide stars and a modal tomography approach is adopted to implement three- dimensional wavefront restorations. The principle of modal tomography is briefly re- viewed and a numerical simulation model is built with three equivalent turbulent lay- ers and a different number of guide stars. Our simulation results show that at least six guide stars are required for an accurate wavefront reconstruction in the case of three layers, and only three guide stars are needed in the two layer case. Finally, eigen- mode analysis results are given to reveal the singular modes that cannot be precisely retrieved in the tomography process.

关键词： instrumentation: multi-conjugate adaptive optics -- tomography

Liquid phase in-situ synthesis of LiF coated boron powder composite and performance study

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Defence Technology（防务技术） 2020年第3期16卷 635-641页

作者： Yang Xu qing-zhong Cui Cheng-wen Zhao State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China Shanxi Jiangyang Chemical Factory Shanxi 030000China

Among practical metal additives,boron(B) has a high volumetric heating value,making it a promising choice as a fuel *** B can theoretically yield a large amount of energy upon complete combustion,its combustion is retarded by the initial presence of B oxide,which coats the surfaces of B *** improve the ignition and combustion properties of B powder,LiOH and NH4F were used as precursors to synthesize uniformly LiF-coated B composites(LiF-B) in *** LiF-B mixture was also prepared for comparison using a physical method.X-ray diffraction(XRD),Fourier-transform infrared(FTIR),scanning electron microscope(SEM),and energy-dispersive X-ray spectroscopy(EDS) were used to characterize the morphologies and compositions of the *** thermal and combustion properties of the samples were characterized by thermal gravity-differential thermal gravity(TG-DTG),differential scanning calo rimetry(DSC) and closed bomb *** XRD,FTIR,SEM and EDS results demonstrated the successful preparation of the coated LiF-B *** TG-DTG and closed bomb experiment results indicated that the addition of LiF decreased the ignition temperature of B powder,and increasing its reaction *** results show that when LiF-B was added,the released heat of underwater explosive increased by 6727.2,7280.4 and 3109.6 J/g at heating rates of 5,10,and 15℃/min,***,LiF-B decreased the activation energy of secondary combustion reaction of explosive system as calculated through Kissinger’s method by 28.9%,which indicated an excellent catalytic effect for the thermal decomposition of underwater *** results reveal that LiF can improve the combustion efficiency of B powder,thereby increasing the total energy of *** mechanical sensitivity increased slightly after adding LiF-B to the underwater *** mpared to the underwater explosive with added B,the mechanical sensitivity of the explosive with added LiF-B was significantly

关键词： Boron LiF Coating Thermal decomposition properties Energy efficiency

All types of base conversions allowed by base editors

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Science China(Life Sciences) 2024年第2期67卷 431-433页

作者： Shun-qing Liang wen Xue RNA Therapeutics Institute UMass Chan Medical SchoolWorcester 01655USA Department of Molecular Cell and Cancer BiologyUMass Chan Medical SchoolWorcester 01655USA Department of Molecular Medicine UMass Chan Medical SchoolWorcester 01655USA Li Weibo Institute for Rare Diseases Research UMass Chan Medical SchoolWorcester 01655USA

Base editors(BEs) hold great promise as tools for introducing single-base-pair changes in both basic research and therapeutic applications(Rees and Liu,2018).Base editors are composed of a Cas9 nickase fused to a DNA-modifying enzyme,which chemically modifies nucleobases within a specific targeting window near the Cas9-binding site.

关键词： base bases allowed

Reliability of the Ultimate Strength of Ship Stiffened Panel Subjected to Random Corrosion Degradation

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China Ocean Engineering 2017年第1期31卷 11-18页

作者： FENG Guo-qing HU Bing-nan ren Hui-long College of Shipbuilding Engineering Harbin Engineering University Harbin 150001 China

Attentions have been increasingly paid to the influence of the corrosion on the ultimate strength of ship structures. In consideration of the random characteristics of the corrosion of ship structures, the method for the ultimate strength analysis of the ship stiffened panel structure subjected to random corrosion degradation is presented. According to the measured corrosion data of the bulk carriers, the distribution characteristics of the corrosion data for the stiffened panel on the midship deck are analyzed, and a random corrosion model is established. The ultimate strength of the corroded stiffened panel is calculated by lhe nonlinear finite element analysis. The statistical descriptions of the ultimate strength of the corroded stiffened panel are defined through the Monte Carlo simulations. A formula is proposed on the ultimate strength reduction of the stiffened panel as a function of the corrosion volume. The reliability analysis of the ultimate strength of the corroded deck stiffened panel is performed. It shows that both the corrosion data of the deck stiffened panel and the ultimate strength of the random corroded deck stiffened panel follow the log-normal distribution. The ultimate stress ratio of the stiffened panel is inversely proportional to the corrosion volume ratio.

关键词： stiffened panel corrosion ultimate strength time variant reliability corrosion volume /:~no- ~T (~ ~11 R NI R^n l-I I. 9017 Rollnhilltvnftho.ltlmnto ~trontrth nf^hl

A low-cost and high-performance technique for adaptive optics static wavefront correction

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Research in Astronomy and Astrophysics 2021年第7期21卷 261-268页

作者： De-qing ren Tian-Yu Zhang Gang Wang California State University Northridge Department of Physics and AstronomyNorthridgeCA 91330USA National Astronomical Observatories/Nanjing Institute of Astronomical Optics and Technology Chinese Academy of SciencesNanjing 210042China CAS Key Laboratory of Astronomical Optics and Technology Nanjing Institute of Astronomical Optics and TechnologyNanjing 210042China University of Chinese Academy of Sciences Beijing 100049China

Non-Common Path Error(NCPE) is one of the factors that limit an Adaptive Optics(AO)system from delivering ultra-high performance. To correct the NCPE associated static aberration, we propose a simple but robust and high-performance pupil-plane based wavefront measurement and correction technique, which can copy a single-mode fiber generated perfect wavefront to the AO system via an iteration optimization process, and the NCPE can be effectively corrected by directly commanding the Deformable Mirror(DM) of the AO system. Compared with the previous focal-plane based approach that uses focal plane based Point Spread Function(PSF) for correction evaluation, the pupil-plane based approach can be reliably and rapidly converged to a global optimization result and provides better performance, in particular for an AO system with a large initial static wavefront error. This technique we proposed can be implemented in astronomical AO systems where extremely high performance is required.

关键词： astronomical instrumentation:adaptive optics astronomical instrumentation:high angular resolution astronomical techniques:high angular resolution