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Discrete element simulation of crushable rockfill materials

Water Science and engineering 2013年第2期6卷 215-229页

作者： Lei SHAO shi-chun CHI Liang-jing ZHOU Yu-zan WANG Faculty of Infrastructure engineering Dalian University of Technology Hydrochina Chengdu engineering Corporation Changjiang Institute of Survey Planning Design and Research Changjiang Water Resources Commission

A discrete element method was used to study the evolution of particle crushing in a rockfill sample subjected to triaxial shear. A simple procedure was developed to generate clusters with arbitrary shapes, which resembled real rockfill particles. A theoretical method was developed to define the failure criterion for an individual particle subjected to an arbitrary set of contact forces. Then, a series of numerical tests of large-scale drained triaxial tests were conducted to simulate the behaviors of the rockfill sample. Finally, we examined the development of micro-characteristics such as particle crushing, contact characteristics, porosity, deformation, movement, and energy dissipation. The simulation results were partially compared with the laboratory experiments, and good agreement was achieved, demonstrating that the particle crushing model proposed can be used to simulate the drained triaxial test ofrockfill materials. Based on a comparison of macro behaviors of the roekfill sample and micro structures of the particles, the microscopic mechanism of the rockfill materials subjected to triaxial shear was determined qualitatively. It is shown that the crushing rate, rather than the number of crushed particles, can be used to reflect the relationship between macro- and micro-mechanical characteristics of rockfill materials. These research results further develop our understanding of the deformation mechanism of rockfill materials.

关键词： discrete element simulation triaxial shear test," roclcfill material geometric construction of particles particle flow code microscopic mechanism

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Stress and thickness calculation of a bolted flat cover with double metal sealing rings

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Nuclear Science and Techniques 2018年第8期29卷 210-217页

作者： Xiao-Yan Wang shi-Feng Zhu Xiao Wang Xiao-chun Zhang Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

The design of a bolted flat cover is extremely important for the structural integrity of pressure *** present design codes provide the thickness calculation equations for a bolted flat cover with single metal ***,the rules for a bolted flat cover with double metal sealing rings are not developed to *** the study,a new thickness calculation equation for the bolted flat cover with double metal sealing rings is ***,the theoretical stress solution for bolted flat cover with the double metal sealing rings is obtained,based on the theory of simply supported circular plate and then verified using the results from finite element *** results indicate that the influence of double metal sealing ring on the stress of the flat cover is more serious compared to single metal ***,a more accurate and reasonable equation is proposed to calculate the thickness of bolted flat cover with double metal sealing rings based on the derived theoretical equations of maximum ***,the influence of linear load and the spacing between rings on the thickness are ***,a few suggestions are provided to design low-pressure or atmosphere pressure *** study provides a theoretical foundation to develop design codes of pressure vessels in nuclear reactors.

关键词：厚度计算扁平金属封面戒指应力和计算方程压力解

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Self-assembly of insulated molecular wires of a water-soluble cationic PPV and anionic dendrons

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Chinese Science Bulletin 2009年第14期54卷 2451-2456页

作者： FeNG XueLing YAO ZhiYi LI chun shi Gao Quan Key Laboratory of Bio-organic Phosphorous Chemistry and Chemical Biology Department of Chemistry Tsinghua University Beijing 100084 China

Insulated molecular wires of poly(phenylenevinylene) (PPV) were prepared by wrapping the conjugated backbones with dendrons through a noncovalent approach. It was found that electrostatic interaction between the quaternary ammonium groups of PPV-1 and the carboxylate moieties in dendrons induced the packing of dendrons along PPV-1 conjugated backbones. Absorption and emission spectroscopic examinations in solution and solid film indicated that the PPV-1 backbones adopted a more planar and isolated conformation in the complexes. Furthermore, interchain interactions in the complexes could be greatly reduced, improving the quantum yield of PPV-1.

关键词：导线绝缘乙烯分子阴离子阳离子水溶性自组装静电相互作用

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Thermoelectric transport across graphene/hexagonal boron nitride/graphene heterostructures

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Nano Research 2015年第2期8卷 666-672页

作者： chun-chung Chen Zhen Li Li shi Stephen B. Cronin Department of electrical engineering University of Southern California Los Angeles CA 90089 USA Department of Mechanical engineering and Texas Materials Institute University of Texas at Austin Texas 78712 USA

We report thermoelectric transport measurements across a graphene/hexagonal boron nitride （h-BN）/graphene heterostructure device. Using an AC lock-in technique, we are able to separate the thermoelectric contribution to the I-V characteristics of these important device structures. The temperature gradient is measured optically using Raman spectroscopy, which enables us to explore thermoelectric transport produced at material interfaces, across length scales of just 1-2 nm. Based on the observed thermoelectric voltage （AV） and tem- perature gradient （AT）, a Seebeck coefficient of -99.3 μV/K is ascertained for the heterostructure device. The obtained Seebeck coefficient can be useful for understanding the thermoelectric component in the cross-plane I-V behaviors of emerging 2D heterostructure devices. These results provide an approach to probing thermoelectric energy conversion in two-dimensional layered heterostructures.

关键词： graphene boron nitride 2D materials heterostructure thermoelectric

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Dewetting Kinetics of Thin Polymer Films with Different Architectures:effect of Polymer Adsorption

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Chinese Journal of Polymer Science 2018年第8期36卷 984-990页

作者： Li-Na Wang Huan-Huan Zhang Lin Xu Bin-Yuan Liu Tong-Fei shi shi-chun Jiang Li-Jia An School of Materials Science and engineering Tianjin University State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of Sciences Laboratory of Surface Physics and Chemistry Guizhou Education University Department of Polymer Science and engineering Hebei University of Technology

We have investigated the influence of the adsorption process on the dewetting behavior of the linear polystyrene film （LPS）, the 3-arm star polystyrene film （3SPS） and the ring polystyrene film （RPS） on the silanized Si substrate. Results show that the adsorption process greatly influences the dewetting behavior of the thin polymer films. On the silanized Si substrate, the 3SPS chains exhibit stronger adsorption compared with the LPS chains and RPS chains; as a result, the wetting layer forms more easily. For LPS films, with the decrease of annealing temperature, the kinetics of polymer film changes from exponential behavior to slip dewetting. As a comparison, the stability of 3SPS and RPS films switches from slip dewetting to unusual dewetting kinetic behavior. The adsorbed nanodroplets on the solid substrate play an important role in the dewetting kinetics by reducing the driving force of dewetting and increase the resistant force of dewetting. Additionally, Brownian dynamics （BD） simulation shows that the absolute values of adsorption energy （ε） gradually increase from linear polymer （-0.3896） to ring polymer （-0.4033） and to star polymer （-0.4264）, which is consistent with the results of our adsorption experiments.

关键词： Thin polymer film Star polystyrene Ring polystyrene Dewetting Adsorption

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Science Letters:Determination of benzalkonium chloride in viscous ophthalmic drops of azithromycin by high-performance liquid chromatography

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2009年第12期10卷 877-882页

作者： Yan SHeN Sheng-jie XU shi-chun WANG Jia-sheng TU Department of Pharmaceutics China Pharmaceutical University Nanjing 210009 China Productivity Center of Jiangsu Province Nanjing 210042 China

A high-performance liquid chromatography （HPLC） system was used in the reversed phase mode for the determination ofbenzalkonium chloride （BKC） in azithromycin viscous ophthalmic drops. A Venusil-XBP（L）-C18 （150 mm×4.6 mm, 5 gm） column was used at 50℃. The mobile phase consisted of a mixture of methanol-potassium phosphate （16：5, v/v）. Two sample preparation methods were compared. The results suggested that, compared with an extraction procedure, a deproteinization procedure was much quicker and more convenient. Using the deproteinization procedure for sample preparation, calibration curves were linear in the range 5.0-50μg/ml. The within-day and inter-day coefficients of variation were less than 10%. The average recoveries were determined as 96.70%, 98.52%, and 97.96% at concentrations of 10.0, 30.0, and 50.0 μg/ml, respectively. Variability in precision did not exceed 5%. In conclusion, this HPLC method using a simple sample treatment procedure appears suitable for monitoring BKC content in azithromycin viscous ophthalmic drops.

关键词： Benzalkonium chloride High-performance liquid chromatography Azithromycin Viscous ophthalmic drops

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Optical Spectroscopy Properties of KMgF_3 :eu^(2+) Nanocrystals and Powder Synthesized by Microemulsion and Solvothermal Process

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Chemical Research in Chinese Universities 2006年第4期22卷 423-426页

作者： HUA Rui-nian SUN Hong-jie JIANG Hui-ming shi chun-shan College of Life Science Dalian Nationalities University Dalian 116600 P. R. China Key Laboratory of Rare earth Chemistry and Physics Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun 130022 P. R. China

Nanocrystals and powders of KMgF3 doped with eu^2＋ were synthesized by the microemulsion method and the selvothermal process, respectively. The emission and excitation spectra of KMgF3： eu^2＋ phosphors were measured and compared with those of the samples synthesized through a solid state reaction, Bridgman-Stockbarger method, and mild hydrothermal technique. The KMgF3： eu^2＋ samples synthesized by means of the microemulsion method and the solvothermal process show only a sharp emission peak located at 360 nm in the emission spectra, which arises from the f→f（ ^6P7/2→^8S7/2 ） transition of eu^2＋ The broad emission bands appear at 420 nm, which arises from eu^2＋←O^2- cannot be observed（ in the mild hydrothermal and single crystal samples, the emission peak at 420 nm besides the emission of eu^2＋ at 360 nm is observed）. In the excitation spectrum of the KMgF3 ： eu^2＋ samples synthesized by the microemulsion method and the solvothermal process, the excitation peaks show an intensive blue shift. The blue shift can be attributed to the lower oxygenic content in the KMgF3 ： eu^2＋ samples synthesized by the microemulsion method and the selvothermal process.

关键词： KMgF3 : eu( Ⅱ ) phosphor Optical property Microemulsion Solvothermal process Nanocrystal

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Precipitation Kinetics of Cr_2N in High Nitrogen Austenitic Stainless Steel

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Journal of Iron and Steel Research International 2008年第6期15卷 72-77页

作者： shi Feng WANG Li-jun CUI Wen-fang LIU chun-ming School of Materials and Metallurgy Northeastern University Shenyang 110004 Liaoning China

The precipitation behavior of Cr2 N during isothermal aging in the temperature range from 700 ℃ to 950 ℃ in Fe-18Cr-12Mn-0.48N （in mass percent） high nitrogen austenitic stainless steel, including morphology and content of precipitate, was investigated using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The isothermal precipitation kinetics curve of Cr2 N and the corresponding precipitation activation energy were obtained. The results show that Cr2N phase precipitates in a cellular way and its morphology is transformed from initial granular precipitates to lamellar ones in the cell with increasing aging time. The nose temperature of Cr2 N precipitation is about 800 ℃, with a corresponding incubation period of 30 min, and the ceiling temperature of Cr2N precipitation is 950℃. The diffusionactivation energy of Cr2 N precipitation is 296 kJ/mol.

关键词： high nitrogen austenitic stainless steel isothermal aging precipitation kinetics precipitation activation energy

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Pressure effects on Thermodynamics of Phase Behavior in Polystyrene/Methylcyclohexane Solutions

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Chemical Research in Chinese Universities 2007年第5期23卷 613-621页

作者： LI Hong-fei JIANG shi-chun AN Li-jia YU Dong-hong State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun 130022 P. R. China Section of Chemistry Department of Life Sciences Aalborg University Aalborg DK 9000 Denmark

The calculations presented in this paper are based on the Sanchez-Lacombe（SL）lattice fluid *** interaction energy parameter,g12/k,required in this approach was obtained by fitting the cloud points of polystyrene（PS）/methylcyclohexane（MCH）polymer solutions under *** SL lattice fluid theory was used to calculate the spinodals,the binodals,and the Flory-Huggins（FH）interaction parameter of the *** calculated results show that the SL lattice fluid theory can describe the dependences of thermodynamics of PS/MCH solutions on temperature and pressure very ***,the calculated enthalpy and the excess volume changes indicate that the Clausius-Clapeyron equation cannot be suitable to describe pressure effect on PS/MCH *** analysis on the thermodynamics of this system under pressure shows that the role of entropy is more important than the excess volume in the present case.

关键词： PS/MCH polymer solution Thermodynamics Pressure effect

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Creep damage characterization of UNS N10003 alloy based on a numerical simulation using the Norton creep law and Kachanov–Rabotnov creep damage model

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Nuclear Science and Techniques 2019年第4期30卷 114-122页

作者： Xiao-Yan Wang Xiao Wang Xiao-chun Zhang shi-Feng Zhu Shanghai Institute of Applied Physics Chinese Academy of Sciences University of Chinese Academy of Sciences

The calculation of inelastic creep damage is important for the structural integrity evaluation of the elevated temperature structure in a thorium molten salt reactor(TMSR). However, a creep damage theory model and numerical simulation method have not been proposed for the key materials(UNS N10003 alloy) in the TMSR. In this study, creep damage characterization of UNS N10003 alloy is investigated using the Norton creep law and Kachanov–Rabotnov(K–R) creep damage model. First, the creep experimental data of the UNS N10003 alloy at 650 °C were adopted to fit the material constants of the two models. Then, the creep damage behavior of the UNS N10003 alloy was analyzed and discussed under uniaxial and multi-axial stress states. The results indicated that the K–R creep damage model is more suitable for the UNS N10003 alloy than the Norton model. Finally, the numerical simulation method was developed by a user-defined UMAT subroutine and subsequently verified through a finite element analysis(FeA). The FeA results were in agreement with the theoretical solutions. This study provides an effective method for the inelastic creep damage analysis of the elevated temperature structure in the TMSR.

关键词： Thorium molten salt reactor UNS N10003 alloy Creep damage Inelastic analysis elevated temperature structure

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