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        Structural Design and Optimization of the Crossbeam of a Computer Numerical Controlled Milling-Machine Tool Using Sensitivity Theory and NSGA-II Algorithm

        Xueguang Li,Chongqing Li,Penghui Li,Huizhong Hu,Xiansheng Sui 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.2

        The crossbeam plays a vital role in computer numerical controlled milling machines, especially in machines with a gantry structure, as it directly influences the machining precision. In this study, a machine tool crossbeam was designed, and the modal frequency of the crossbeam was analyzed using the finite element model (FEM) analysis. In the improved structure obtained through FEM analysis, the X-type structure of the internal unit of the crossbeam was replaced by an O-type structure. The specific structure dimensions were further optimized using a neural-network algorithm and a nondominated sorting genetic algorithm. Finally, we calculated the effect of each crossbeam dimension on the mass, deformation, and frequency in a sensitivity analysis. After optimizing the crossbeam dimensions with respect to deformation, modal frequency, and mass, the structural characteristics of the original and optimized crossbeams were compared. After optimization, the mass and deformation were reduced by 7.45% and 3.08%, respectively, and the modal frequency was increased by 0.42%. These results confirm that the optimization improved the performance of the crossbeam structure.

      • Setup and Performance of a Combined Hardware-in-loop and Software-in-loop Test for MMC-HVDC Control and Protection System

        Chang Lin,Dong Liu,Xueguang Wu,ZhiyuanHe,Weihua Wang,Wei Li 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

        Despite the rapid development of VSC-HVDC technology, the practical experience to operate modular multi-level converter (MMC) has not yet been sufficiently accumulated. Real-time simulation is one of the most efficient approaches to verify the control and protection (C & P) scheme under various contingencies. With the increasing number of sub-modules, the accurate simulation of the MMC-HVDC becomes more difficult, as it requires larger computing resources and more complex interface between the test platform and the C&P system hardware devices. This paper proposes an application of real-time simulation, which combines the hardware-in--loop (HIL) and software-in-loop (SIL) approach to test a control and protection system for MMC-based HVDC links. In the proposed system, a pole control and protection (PCP) will be tested using the HIL approach, while the valve base controller (VBC) is tested using the SIL method. The setup of the test rig and performance is demonstrated in this paper.

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        Tissue Inhibitor of Metalloproteinase-1 Pro-motes NIH3T3 Fibroblast Proliferation by Activating p-Akt and Cell Cycle Progression

        Yang Lu,Shuxin Liu,Shujia Zhang,Guangyan Cai,Hongwei Jiang,Huabin Su,Xiaofan Li,Quan Hong,Xueguang Zhang,Xiangmei Chen 한국분자세포생물학회 2011 Molecules and cells Vol.31 No.3

        Tissue inhibitor of metalloproteinase-1 (TIMP-1) plays various roles in cell growth in different cell types. However, few studies have focused on TIMP-1’s effect on fibroblast cells. In this study, we investigated the effects of TIMP-1 overexpression on NIH3T3 fibroblast proliferation and potential transduction signaling pathways involved. Overexpression of TIMP-1, by transfection of the pLenti6/ V5-DESTTIMP-1 plasmid, significantly promoted NIH3T3 proliferation as determined by the BrdU array. Neither 5 nor 15 nM GM6001 (matrix metalloproteinase system inhibitor) affected NIH3T3 proliferation, but 45 nM GM6001 inhibited proliferation. TIMP-1 overexpression activated the p-Akt pathway, but not the p-ERK or p-p38 pathway. In TIMP-1-transfected cells, cyclinD1 was upregulated and p21CIP1 and p27^(KIP1) were downregulated, which promoted cell entry into the S and G2/M phases. The PI3-K inhibitor LY294002 abolished the TIMP-1-induced effects. Overexpression of intracellular TIMP-1 stimulated NIH3T3 fibroblast proliferation in a matrix metalloproteinase (MMP)-independent manner by activating the p-Akt pathway and related cell cycle progression.

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