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NUMERICAl SIMUlATION OF SUCCINONITRITE DENDRITIC GROWTH IN A FORCED FlOW

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Acta Metallurgica Sinica(English letters) 2008年第6期21卷 444-450页

作者： Z. chen C.l. chen l.M. Hao School of Science Department of Applied Physics Shaanxi Key Laboratory of Condensed Matter Structures and Properties Northwestern Polytechnical University Xi＇an 710072 China School of Science Xi＇an University of Science ＆ Technology Xi＇an 710054 China

Numerical simulation based on phase field method is performed to describe solidification process of pure material in a free or forced flow. The evolution of the interface is showed, and the effects of mesh grid and flow velocity on succinonitrite shape are studied. These results indicate that crystal grows into an equiaxial dendrite in a free flow and into an asymmetrical dendritic in a forced flow. With increasing flow velocity, the upstream dendritic arm tip grows faster and the downstream arm grows slower. However, the evolution of the perpendicular tip has no significant change. In addition, mesh grid has no influence on dendritic growth shape when mesh grid is above 300×300.

关键词： Phase field method Forced flow Dendritic Succinonitrite Tip velocity

INTERNAl FRICTION AND ElASTIC CONSTANTS OF Pd-B-H AllOYS

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Acta Metallurgica Sinica(English letters) 1998年第1期11卷 51-55页

作者： Y.l.chen Zhejiang Univ Hangzhou China

Internal friction measurements on binary and ternary α-phase alloys of Pd with hydrogen and boron have been performed with a torsion pendulum and by observing the cttenuation of ultrasonic pulses. A pronounced damping maximum of binary Pd-B alloys at 220K and measuring frequencies of about 4Hz could not be established at a frequency of 15MH. Ternary Pd-B-H alloys show an additional damping maximum besides the hydrogen Zener effect, which is interpreted in terms of a changed jump frequency of hydrogen in the neighborhood of boron atoms.

关键词： Pd-B-H alioy,internal friction,elastic constant Zener effect

Tensile and cyclic deformation response of friction-stir-welded dissimilar aluminum alloy joints:Strain localization effect

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Journal of Materials Science & Technology 2021年第14期73卷 91-100页

作者： P.l.Niu W.Y.li D.l.chen State Key laboratory of Solidification Processing Shaanxi Key Laboratory of Friction Welding TechnologiesNorthwestern Polytechnical UniversityXi'an710072.China Department of Mechanical and Industrial Engineering Ryerson University350 Victoria StreetTorontoOntarioM5B2K3Canada

Cyclic deformation behavior of friction-stir-welded dissimilar AA2024-T351 to AA7075-T65 aluminum alloy joints was evaluated via stepwise tests at different strain rates,along with transmission electron microscopy examinations to characterize the precipitates required to assess internal *** backscatter diffraction was employed to observe the inhomogeneous microstructures of the FSWed *** localization appeared in the heat affected zone(HAZ)of AA2024 *** cyclic deformation of 500 cycles at a total strain amplitude of 0.5%,the strength of the dissimilar joints resumed basically to that of AA2024 base *** the AA2024 HAZ was obviously hardened,which should be attributed to the introduced dislocations during cyclic deformation *** hardening capacity of the joints increased with decreasing strain rate.

关键词： Friction stir welding Dissimilar aluminum alloys Strain localization Cyclic hardening Slip irreversibility

Finite element implementation of strain-hardening Drucker-Prager plasticity model with application to tunnel excavation

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Underground Space 2017年第3期2卷 168-174页

作者： K.liu S.l.chen Department of Civil&Environmental Engineering Louisiana State UniversityBaton RougeLAUSA

This paper presents a finite element implementation of a strain-hardening Drucker-Prager model and its application to tunnel *** computational model was constructed based on the return mapping scheme,in which an elastic trial step was first executed,followed by plastic correction involving the Newton-Raphson method to return the predicted state of stresses to the supposed yield *** combining the plastic shear hardening rule and stress correction equations,the loading index for the strain-hardening Drucker-Prager model was *** is therefore possible to update the stresses,elastic and plastic strains,and slope of the yield locus at the end of each incremental *** an illustrative example,an integration algorithm was incorporated into ABAQUS through the user subroutine UMAT to solve the tunnel excavation problem in strain-hardening Drucker-Prager rock *** obtained numerical results were found to be in excellent agreement with the available analytical solutions,thus indicating the validity and accuracy of the proposed UMAT code,as well as the finite element model.

关键词： Strain-hardening Drucker-Prager model Finite element method UMAT code Tunnel excavation

A Multiple Feature Approach for Disorder Normalization in Clinical Notes

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维普期刊数据库

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Wuhan University Journal of Natural Sciences 2016年第6期21卷 482-490页

作者： lü chen chen Bo lü Chaozhen QIU likun JI Donghong School of Computer Wuhan University Department of Chinese language and literature Hubei University of Art and Science Shandong Key lab of language Resource Development and Application Ludong University

In this paper we propose a multiple feature approach for the normalization task which can map each disorder mention in the text to a unique unified medical language system（UMlS）concept unique identifier（CUI）. We develop a two-step method to acquire a list of candidate CUIs and their associated preferred names using UMlS API and to choose the closest CUI by calculating the similarity between the input disorder mention and each candidate. The similarity calculation step is formulated as a classification problem and multiple features（string features,ranking features,similarity features,and contextual features） are used to normalize the disorder mentions. The results show that the multiple feature approach improves the accuracy of the normalization task from 32.99% to 67.08% compared with the Meta Map baseline.

关键词： natural language processing disorder normalization levenshtein distance semantic composition multiple features

ANTIPERIODIC WAVElETS

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Journal of Computational Mathematics 1996年第1期14卷 32-39页

作者： H.l. chen(Institute of Mathematics, Academia Sinica, Beijing) ACAD SINICA INST MATHBEIJING 100080PEOPLES R CHINA

In this paper, we construct the orthogonal wavelet basis in the space of antiperiodic functions by appealing the spline methods. Differing from other results in papers([1,2,3,6,8]), here we derive the 3-scale equation, by using this equation we construct some basic functions, those functions can be used to construct different orthonormal basis in some spline function spaces.

关键词： Math ANTIPERIODIC WAVElETS Pro

STRAIN RATE SENSITIVITY OF UlTRAFINE-GRAINED Cu WITH NANOSIZED TWINS

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Acta Metallurgica Sinica(English letters) 2006年第5期19卷 313-318页

作者： l.X. liu X.H. chen l. lu Shenyang National laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

An ultrafine-grained Cu sample with a high density of growth twins was synthesized by means of pulsed electrodeposition technique. The strain rate sensitivity of the Cu sample was measured by strain rate cycling tests under tension. The effects of grain size as well as twin density on the strength and strain rate sensitivity were discussed.

关键词： copper nanosized twin strain rate sensitivity deformation mechanism

Economic optimization of resource-constrained project scheduling:a two-phase metaheuristic approach

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Journal of Zhejiang University-Science C(Computers and Electronics) 2010年第6期11卷 481-494页

作者： Angela H.l.chen Chiuh-cheng CHYU Department of Industrial Engineering and Management Yuan Ze University Department of Finance Nanya Institute of Technology

This paper deals with the problem of project scheduling subject to multiple execution modes with non-renewable resources, and a model that handles some of monetary issues in real world *** objective is to schedule the activities to maximize the expected net present value(NPV) of the project, taking into account the activity costs, the activity durations, and the cash flows generated by successfully completing an *** to the combinatorial nature of this problem, the current study develops a hybrid of branch-and-bound procedure and memetic algorithm to enhance both mode assignment and activity *** for the makespan minimization problem have been made through a set of benchmark problem *** performance is rated on the maximization of the project NPV and computational results show that the two-phase hybrid metaheuristic performs competitively for all instances of different problem sizes.

关键词： Memetic algorithm(MA) Branch and bound(B&B) algorithm Net present value(NPV) Project scheduling problem

EFFECT OF TESTING ENVIRONMENT ON FRACTURING BEHAVIOR OF Fe_3Si BASED AllOY

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Acta Metallurgica Sinica(English letters) 2003年第2期16卷 104-109页

作者： J.H.Peng G.l.chen National Key laboratory for Nuclear Fuel&Materials China Nuclear Power InstituteChengdu 610041ChinaState Key Laboratory for Advanced Metal MaterialsUniversity of Science&Technology BeijingBeijing 100083China

The mechanical behavior of Fes Si based alloy with B2 structure was studied by tension and fracture toughness test in various testing media. The fracture strength σb of Fe3Si alloy decreased in the following order: oxygen, air and hydrogen respectively. The fracture toughness in different testing environment showed that KIC in oxygen is 11.5±0.3MPa·m1/2, and is 8.6±0.4MPa·ml/2 in distilled water. The reduction of fracture toughness is contributed to the environmental reaction of Si with water. Addition of Al element in Fe3Si is not beneficial to improve the intrinsic ductility of Fe-14Si-3Al alloy. The scattering phenomenon of fracture strength was found, and explained by fracture mechanics. It was found by means of SEM that the fracture mode changed from transgranular in oxygen to intergranular in hydrogen gas and distilled water.

关键词： Fe3Si intermetallic mechanical behavior environmental em- brittlement