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      • KCI등재

        Study of the Flow Behavior and Defect Formation in Forming of Axisymmetrically Flanged and Multi-Scaled Parts

        Ji Lai Wang,Ming Wang Fu,Junxi Yu,Xing Wang,Wenbin Yang 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.10

        In microforming, the quality of microparts is one of the most critical issues. Folding caused by the abnormal material flow is one of the most common flow-induced defects in macroforming process. The identified formation mechanism of flow-induced defects in macro-forming process could be affected by the so-called size effects when the part dimension is scaled down to micro scale. Therefore, it is necessary to investigate the influence of size effects on the material plastic flow and deformation behavior in multiscaled deformation scenarios. To explore the formation mechanism of flow-induced defects, FE simulation is used to simulate the forming process. On the other hand, the multi-scaled forming was designed. To study the relationship of the flow-induced defect and sizes effects, forming of the axisymmetric parts with flanged features and different scales was conducted. The microstructure and plastic flow behavior of the deformed parts are also revealed. Based on the experimental and FEM simulation results, the formation of folding defects is mainly affected by the geometries and the sizes of the deformed flanged parts instead of grain sizes. In the cases by using material with coarse grains, the folding defect can be significantly reduced.

      • SCOPUSKCI등재

        CCl<sub>4</sub> Activation Mechanisms by Gas-Phase CHBr<sup>•</sup><sup>–</sup> and CBr<sub>2</sub><sup>•</sup><sup>–</sup>: A Comparative Study

        Liang, Junxi,Wang, Yanbin,Hasi, Qimeige,Geng, Zhiyuan Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.2

        The mechanisms concerning C-Cl activation of $CCl_4$ by $CHBr^{{\cdot}-}$ and $CBr{_2}^{{\cdot}-}$ have been comparatively investigated in theory. Optimized geometries and frequencies of all stationary points on PES are obtained at the BhandHLYP/aug-cc-pVTZ level of theory, and then the energy profiles are refined at the QCISD(T) method with the aug-cc-pVTZ basis by using the BhandHLYP/aug-cc-pVTZ optimized geometries. Our calculated findings suggest that in the title reactions the major mechanisms consist of both Cl-abstraction and $S_N2$ substitution reactions. Also, a succeeding pathway described by electron transfer was revealed before the initial Cl-abstraction products separate. Those are consistent with relevant experimental results.

      • KCI등재

        Cl4 Activation Mechanisms by Gas-Phase CHBr•– and CBr2•–: A Comparative Study

        Liang Junxi,Wang Yanbin,Qimeige Hasi,Geng Zhiyuan 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.2

        The mechanisms concerning C-Cl activation of CCl4 by CHBr•– and CBr2 •– have been comparatively investigated in theory. Optimized geometries and frequencies of all stationary points on PES are obtained at the BhandHLYP/aug-cc-pVTZ level of theory, and then the energy profiles are refined at the QCISD(T) method with the aug-cc-pVTZ basis by using the BhandHLYP/aug-cc-pVTZ optimized geometries. Our calculated findings suggest that in the title reactions the major mechanisms consist of both Cl-abstraction and SN2 substitution reactions. Also, a succeeding pathway described by electron transfer was revealed before the initial Cl-abstraction products separate. Those are consistent with relevant experimental results.

      • KCI등재

        DIESEL HYBRID ELECTRIC VEHICLE HARDWARE SYSTEM

        Song Junhua,Wang Junxi,Zhuo Bin,H. B. TANG,X. J. MAO 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.4

        A controller for a diesel hybrid electric vehicle based on a V-cycle development approach is investigated in this paper. The hardware and infra program of the Hybrid Control Unit (HCU) are discussed in detail. The hardware system is designed based on circuit simulation; while the infra system is written with assemble language. Time sharing mode, buffer sharing mode and multi-task schedule method are used to ensure real-time communication in the infra program design. Based on multi-thread technology, hardware in loop test system is also designed. The hardware in loop and bench tests show that the controller could meet the requirements of the hybrid electric vehicle (HEV) and communicate in real-time. Circuit simulation, HCU, infra program and hardware in loop test form the effective V-cycle development platform to design a hardware system for a diesel HEV controller. A controller for a diesel hybrid electric vehicle based on a V-cycle development approach is investigated in this paper. The hardware and infra program of the Hybrid Control Unit (HCU) are discussed in detail. The hardware system is designed based on circuit simulation; while the infra system is written with assemble language. Time sharing mode, buffer sharing mode and multi-task schedule method are used to ensure real-time communication in the infra program design. Based on multi-thread technology, hardware in loop test system is also designed. The hardware in loop and bench tests show that the controller could meet the requirements of the hybrid electric vehicle (HEV) and communicate in real-time. Circuit simulation, HCU, infra program and hardware in loop test form the effective V-cycle development platform to design a hardware system for a diesel HEV controller.

      • KCI등재

        Impact of DFIG-Based WTs on Subsynchronous Oscillation Damping of SG Based on the Net Electrical Damping Method

        Jia Qi,Gangui Yan,Liu Kan,Hu Wenbo,Wang Junxi 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.2

        Subsynchronous oscillations (SSOs) induced during the generation of wind power constitute an important problem that aff ects the safety and the stability of power systems. It is useful to study the impact of wind turbines on the damping of the SSOs of a synchronous generator (SG). On the one hand, the relevant studies have been based mainly on eigenvalue analysis, which is insuffi cient, and on the other, an examination of the general mechanism of the SSO is still lacking. Based on the net electrical damping analysis method, this paper examines the dynamic interaction between the SG and doubly fed induction generator-based wind turbines (DFIGs). The self-stabilizing damping coeffi cient and the mutually stabilizing damping coeffi cient are proposed from the perspective of the SG, and the eff ects of diff erent numbers and current loop control parameters of the DFIGs on torsional modes of the SG are analyzed using diff erent grid structures. A time-domain simulation model of DFIGs connected to a power grid is built in EMTDC/PSCAD to verify the correctness of the theoretical analysis.

      • KCI등재

        Analysis of Subsynchronous Oscillation of Direct Drive PMSG Based Wind Farm Under Low Operating Condition

        Qi Jia,Gangui Yan,Wenbo Hu,Kan Liu,Junxi Wang 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.1

        Aiming at the sub-synchronous oscillation (SSO) problem that direct-drive permanent magnetic synchronous generator (PMSG) based wind farm under low operating conditions connects to the grid, based on the idea of graphical block modeing, the wind turbine generation (WTG), collector circuit and grid are regarded as discrete components. On the basis of establishing detailed models of each component, two linearized models of direct-drive PMSG based wind farm under different collector circuit topological structure is constructed. Wind farm impedance model is constructed based on state space equation of linearized model. The infl uences of current inner loop control parameters, grid strength, operating conditions on SSO characteristics are analysed. The diff erence between the two models in the study of SSO is compared. Finally, a time-domain simulation model of direct drive PMSG based wind farm connected to grid is built in EMTDC/PSCAD and the validity of the theoretical analysis is verifi ed.

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