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Interfacial microstructure evolution and bonding mechanisms of 14YWT alloys produced by hot compression bonding

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Journal of Materials Science & Technology 2019年第8期35卷 1671-1680页

作者： Liying Zhou Shaobo Feng Mingyue Sun bin xu Dianzhong Li Shenyang National Lab. for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Materials Science and Engineering University of Science and Technology of China Shenyang 110016 China

Hot compression bonding was first used to join oxide-dispersion-strengthened ferrite steels(14 YWT)under temperatures of 750–1100℃ with a true strain range of 0.11–0.51. Subsequently, the microstructure evolution and mechanical properties of the joints were characterized, revealing that the 14 YWT steels could be successfully bonded at a temperature of at least 950℃ with a true strain of 0.22, without degrading the fine grain and nanoparticle distribution, and the presence of inclusions or micro-voids along the bonding interface. Moreover, the joints had nearly the same tensile properties at room temperature and exhibited a similar fracture morphology with sufficient dimples compared to that of the base material. An electron backscattered diffraction technique and transmission electron microscopy were systematically employed to study the evolution of hot deformed microstructures. The results showed that continuous dynamic recrystallization characterized by progressive subgrain rotation occurred in this alloy, but discontinuous dynamic recrystallization characterized by strain-induced grain boundary bulging and subsequent bridging sub-boundary rotation was the dominant nucleation mechanism. The nuclei will grow with ongoing deformation, which will contribute to the healing of the original bonding interface.

关键词： Oxide dispersion strengthened steels Hot compression bonding Dynamic recrystallization Tensile property

Numerical analysis of dislocations of the face slabs of the Zipingpu Concrete Faced Rockfill Dam during the Wenchuan earthquake

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Earthquake Engineering and Engineering Vibration 2011年第4期10卷 581-589页

作者： Kong Xianjing Zhou Yang Zou Degao xu bin Yu Long The State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024 China Institute of Earthquake Engineering School of Hydraulic Engineering Dalian University of Technology Dalian 116024 China

The Zipingpu Concrete Faced Rockfill Dam （CFRD） was obviously damaged during the Wenchuan earthquake in 2008. A wide range of dislocations occurred along the horizontal construction joints at EL. 845m, between the face slabs constructed in the second and third stages. The maximum displacement of the dislocations reached 17cm. In this study, the slab dislocations were investigated using finite element （FE） analysis. The method based on strain potential was applied to compute the permanent deformation of the Zipingpu Dam during the Wenchuan earthquake. The calculated magnitude of the slab dislocation showed good agreements with the field measurements. The dislocation mechanism was discussed. The results show that the dislocation of the concrete slab is a subsequent damage after the permanent deformation of the rockfill materials. The effects of the shear strength and the direction of the construction joints, the reservoir water level and the seismic waves were studied. The shear strength and the direction of the construction joints, reservoir water level and have a significant effect on the dislocation displacement. The dislocation can be effectively reduced by measures such as changing the direction of the construction joints or improving the shear strength at the horizontal joints.

关键词： Zipingpu CFRD construction joints dislocation numerical simulation Wenchuan earthquake

Self-calibration and Compensation of Setting Errors for Surface Profile Measurement of a Microstructured Roll Workpiece

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Chinese Journal of Mechanical Engineering 2014年第1期27卷 14-22页

作者： GAO Wei xu bin TAKEISHI Toshiki SHIMIZU Yuki ITO So Department of Nanomechanics Tohoku University School of Manufacturing Science and Engineering Sichuan University

Microstructured roll workpieces have been widely used as functional components in the precision industries. Current researches on quality control have focused on surface profile measurement of microstructured roll workpieces, and types of measurement systems and measurement methods have been developed. However, low measurement efficiency and low measurement accuracy caused by setting errors are the common disadvantages for surface profile measurement of microstructured roll workpieces. In order to shorten the measurement time and enhance the measurement accuracy, a method for self-calibration and compensation of setting errors is proposed for surface profile measurement of microstructured roll workpieces. A measurement system is constructed for the measurement, in which a precision spindle is employed to rotate the roll workpiece and an air-bearing displacement sensor with a micro-stylus probe is employed to scan the microstructured surface of the roll workpiece. The resolution of the displacement sensor is 0.14 nm and that of the rotary encoder of the spindle was 0.15r~. Geometrical and mathematical models are established for analyzing the influences of the setting errors of the roll workpiece and the displacement sensor with respect to the axis of the spindle, including the eccentric error of the roll workpiece, the offset error of the sensor axis and the zero point error of the sensor output. Measurement experiments are carded out on a roll workpiece on which periodic microstructures are a period of 133 i^m along the circumferential direction. Experimental results demonstrate the feasibility of the self-compensation method. The proposed method can be used to detect and compensate the setting errors without using any additional accurate artifact.

关键词： measurement profile setting error self-calibration compensation microstructure roll workpiece

How Do Pronouns Affect Word Embedding

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Tsinghua Science and Technology 2017年第6期22卷 586-594页

作者： Tonglee Chung bin xu Yongbin Liu Juanzi Li Chunping Ouyang the Department of Computer Science and Technology Tsinghua University Beijing 100084 China the School of Computer Science and Technology University of South China Hengyang 421001 China.

Word embedding has drawn a lot of attention due to its usefulness in many NLP tasks. So far a handful of neural-network based word embedding algorithms have been proposed without considering the effects of pronouns in the training corpus. In this paper, we propose using co-reference resolution to improve the word embedding by extracting better context. We evaluate four word embeddings with considerations of co-reference resolution and compare the quality of word embedding on the task of word analogy and word similarity on multiple data *** show that by using co-reference resolution, the word embedding performance in the word analogy task can be improved by around 1.88%. We find that the words that are names of countries are affected the most,which is as expected.

关键词： word embedding co-reference resolution representation learning

Optimizing evasive maneuvering of planes using a flight quality driven model

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Science China(Information Sciences) 2024年第3期67卷 197-208页

作者： Chang LIU Shaoshan SUN Chenggang TAO Yingxin SHOU bin xu School of Automation Northwestern Polytechnical University Chengdu Aircraft Design & Research Institute of AVIC

This paper investigates the optimal evasive maneuver for a plane to avoid an incoming missile. To accurately model the system dynamics while improving computational efficiency, a simplified plane model based on flight quality is established. A missile model with proportional guidance is also *** problem of determining the optimal evasion plane maneuver is formulated. The Gauss pseudospectral method(GPM) is proposed as a solution to find the optimal maneuver. The optimized maneuver is validated by testing it on a high-fidelity 6-degree-of-freedom(6-DOF) model, which demonstrates the effectiveness of the proposed simplified plane model. The Monte Carlo method is employed to evaluate the capability of the plane to evade missiles in various scenarios and elucidate general principles for successful evasion.

关键词： optimal maneuver flying quality evasive strategy pursuit-evasion game air-to-air combat

Effect of Oscillatory Shear on the Mechanical Properties and Crystalline Morphology of Linear Low Density Polyethylene

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Chinese Journal of Polymer Science 2015年第8期33卷 1114-1124页

作者： Zhong-bin xu Liang-yao Su Peng-fei Wang 彭懋 College of Chemical and Biological Engineering Zhejiang University Department of Polymer Sci & Engn Zhejiang University

In this study, effects of oscillatory shear with different frequencies （0-2.5 Hz） and amplitudes （0-20 mm） on the mechanical properties and crystalline morphology of linear low density polyethylene （LLDPE） were investigated. It was found that the mechanical properties of LLDPE are improved because of the more perfect crystalline structure when LLDPE crystallizes under low-frequency and small-amplitude （0.2 Hz/4 mm） oscillatory shear. The mechanical properties can be further improved by increasing either the frequency or the amplitude of oscillatory shear. The Young＇s modulus and tensile strength of LLDPE are improved by 27% and 20%, respectively, when the frequency is increased to 2.5 Hz and the amplitude is maintained at 4 mm; while the Young＇s modulus and tensile strength are improved by 49% and 47%, respectively, when the amplitude is increased to 20 mm and the frequency is remained as 0.2 Hz. The crystallinity and microstructure of LLDPE under different oscillatory shear conditions were investigated by using differential scanning calorimetry, wide angle X-ray diffraction and scanning electron microscopy to shed light on the mechanism for the improvement of mechanical properties.

关键词： Oscillatory shear Linear low density polyethylene Shish-kebab Mechanical property Crystalline morphology.

A flexible various-scale approach for soil-structure interaction and its application in seismic damage analysis of the underground structure of nuclear power plants

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Science China(Technological Sciences) 2018年第7期61卷 1092-1106页

作者： QU YongQian ZOU DeGao KONG XianJing xu bin YU Xiang The State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology School of Hydraulic Engineering Dalian University of Technology

In simulations of geotechnical engineering, interface elements are versatile tools and are widely used in the modeling of the relative displacements between soils and structures. To consider the case of a local failure adjacent to a soil-structure interaction region, a partial mesh refinement should be performed. In this study, a three-dimensional(3 D) interface element with an arbitrary number of nodes is developed as a new technique to reduce the complexity and difficulty of managing the various scales between soil and structure. An asymmetric number of nodes is permissible on the two sliding surfaces. In this manner, soil and structure can be discretized independently, and the various-scale model is established conveniently and rapidly. The accuracy of the proposed method is demonstrated through numerical examples. The various-scale approach is employed in an elasto-plastic seismic damage analysis of a buried concrete drainage culvert of a nuclear power plant. The results indicate that by applying the proposed method, the number of elements decreased by 72.5%, and the computational efficiency improved by 59% with little influence on accuracy. The proposed method is powerful for local damage evolution analyses of both soil and structure and possesses great practical significance and the potential for further application, especially for nonlinear analysis of large-scale geotechnical engineering.

关键词： 3D interface element soil-structure interaction various-scale underground structure elasto-plastic analysis seismicdamage

Novel supervised classification approach for multifrequency polarimetric SAR data

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Journal of Systems Engineering and Electronics 2015年第6期26卷 1216-1221页

作者： Biao You bin xu Jian Yang Chunmao Yeh Jianshe Song Department of Electronic Engineering Tsinghua University Beijing Institute of Radio Measurement Xi'an Research Institute of Hi-Technology

A novel method is proposed for the supervised classification of multifrequency polarimetric synthetic aperture radar （PolSAR） images. The coherency matrices in P-, L-, and C-bands are mapped onto a 9×9 matrix Ω based on the eigenvalue decomposition of the coherency matrix of each band. A boxcar filter is then performed on the matrix Ω. The filtered data are put into a complex Wishart classifier. Finally, the effectiveness of the proposed method is demonstrated with JPL/AIRSAR multifrequency PolSAR data acquired over the Flevoland area.

关键词： synthetic aperture radar (SAR) polarimetry classifi-cation multifrequency.

Scattering for 3D Cubic Focusing NLS on the Domain Outside a Convex Obstacle Revisited

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Acta Mathematica Sinica,English Series 2022年第6期38卷 1054-1068页

作者： Cheng bin xu Teng Fei ZHAO Ji Qiang ZHENG The Graduate School of China Academy of Engineering Physics Beijing 100088P.R.China School of Mathematics and Physics University of Science and Technology BeijingBeijing 100083P.R.China Institute of Applied Physics and Computational Mathematics P.O.Box 8009Beijing 100088P.R.China

In this article,we consider the focusing cubic nonlinear Schr?dinger equation(NLS)in the exterior domain outside of a convex obstacle in R3with Dirichlet boundary *** revisit the scattering result below ground state in Killip-Visan-Zhang[The focusing cubic NLS on exterior domains in three ***,1,146-180(2016)]by utilizing the method of Dodson and Murphy[A new proof of scattering below the ground state for the 3d radial focusing cubic ***.,145,4859-4867(2017)]and the dispersive estimate in Ivanovici and Lebeau[Dispersion for the wave and the Schr?dinger equations outside strictly convex obstacles and ***.,355,774-779(2017)],which avoids using the concentration *** conquer the difficulty of the boundary in the focusing case by establishing a local smoothing effect of the *** on this effect and the interaction Morawetz estimates,we prove that the solution decays at a large time interval,which meets the scattering criterion.

关键词： Schrodinger equation exterior domain global well-posedness scattering criterion