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      • KCI등재

        Comparison of semi-active and passive tuned mass damper systems for vibration control of a wind turbine

        Eric R. Lalonde,Kaoshan Dai,Girma Bitsuamlak,Wensheng Lu,Zhi Zhao 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.30 No.6

        Robust semi-active vibration control of wind turbines using tuned mass dampers (TMDs) is a promising technique. This study investigates a 1.5 megawatt wind turbine controlled by eight different types of tuned mass damper systems of equal mass: a passive TMD, a semi-active varying-spring TMD, a semi-active varying-damper TMD, a semi-active varying-damper-and-spring TMD, as well as these four damper systems paired with an additional smaller passive TMD near the mid-point of the tower. The mechanism and controllers for each of these TMD systems are explained, such as employing magnetorheological dampers for the varying-damper TMD cases. The turbine is modelled as a lumped-mass 3D finite element model. The uncontrolled and controlled turbines are subjected to loading and operational cases including service wind loads on operational turbines, seismic loading with service wind on operational turbines, and high-intensity storm wind loads on parked turbines. The displacement and acceleration responses of the tower at the first and second mode shape maxima were used as the performance indicators. Ultimately, it was found that while all the semi-active TMD systems outperformed the passive systems, it was the semi-active varying-damper-and-spring system that was found to be the most effective overall – capable of controlling vibrations about as effectively with only half the mass as a passive TMD. It was also shown that by reducing the mass of the TMD and adding a second smaller TMD below, the vibrations near the mid-point could be greatly reduced at the cost of slightly increased vibrations at the tower top.

      • KCI등재

        Electrospun Li2MnO3-Modified Li1.2NixCo0.1Mn0.9-xO2 Nanofibers: Synthesis and Enhanced Electrochemical Performance for Lithium-Ion Batteries

        Jing Yao,Xinlu Wang,Xinru Zhao,Jinxian Wang,Hongbo Zhang,Wensheng Yu,Guixia Liu,Xiangting Dong 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.6

        The Li2MnO3-modified Li1.2NixCo0.1Mn0.9-xO2 (x = 0.2, 0.45, 0.7)as cathode materials for lithium-ion batteries have beensuccessfully synthesized by a simple electrospinning process. Thestructure, morphology and electrochemical performances of theresulting products are studied systematically. The as-preparedLi2MnO3-modified Li1.2NixCo0.1Mn0.9-xO2 (x = 0.2, 0.45, 0.7) with adiameter of 200-300 nm has an initial discharge capacity of168.740 mAh·g−1, coulombic efficiency of 99.6% and a reversiblecapacity as high as 139.016 mAh·g−1 after 200 cycles at a currentrate of 0.2 C. The excellent electrochemical performances ofwhich are attributed to the stabilization of Li2MnO3 structure, therole of Li2MnO3 is contribute extra lithium to the reversiblecapacity and to facilitate Li+ transport through the structure.

      • KCI등재

        Research on effects of key influencing factors upon fuel injection characteristics of the combination electronic unit pump for diesel engines

        Liyun Fan,Quan Dong,Chao Chen,Yun Bai,Wensheng Zhao,Xiuzhen Ma 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.10

        A numerical model of the combination electronic unit pump (CEUP) fuel injection system was developed in AMESim environment. The effects of five key influencing factors, including cam profile velocity, plunger diameter, length of high pressure fuel pipe, inner diameterof high pressure fuel pipe and nozzle flow rate on injection characteristic parameters, were analyzed by using the developed numericalmodel. On the basis, a correlation analysis between the influencing factors and injection characteristics was performed by usingthe design of experiments (DoE) method, and the influences of these factors were quantized accordingly. Relevant results show that boththe single influencing factor and the interaction among these factors correlates with the injection characteristics, and the correlation representsa complex law with the cam rotational speed. The effect of plunger diameter on the injection pressure, cycle fuel injection quantityand injection duration is the most obvious, especially at a cam rotational speed of 500 r/min and the correlation coefficient is up to 0.82. The length of high-pressure pipe (HP pipe) has the most obvious influence on the coefficient of fuel feeding at cam rotational speed of500 r/min and 800 r/min, and the correlation coefficient is negative. Overall, the independent influence of the factors is more significantthan the combined influence of various factors. The CEUP fuel injection system is a complicated multi-input multi-output (MIMO)nonlinear system in fact.

      • KCI등재

        Effect of Minor Sc Addition on the Microstructure Evolution of Al–Cu–Li–Mg Alloy During Homogenization with Different Cooling Modes

        Ya Tang,Daihong Xiao,Lanping Huang,Renxuan You,Xinyue Zhao,Nan Lin,Yunzhu Ma,Wensheng Liu 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.10

        The microstructure evolution and mechanical properties of Al–3.92Cu–1.10Li–0.68Mg–0.32Ag–0.23Mn–0.35Zn–0.11Zrand Al–3.92Cu–1.12Li–0.76Mg–0.29Ag–0.24Mn–0.24Zn–0.12Zr–0.083Sc (wt%) alloys during homogenization with differentcooling modes were comprehensively studied. It was clearly revealed that the minor Sc addition refined the grainsof as-cast Al–Cu–Li–Mg alloys through the formation of primary Al3(Sc, Zr) phases during the solidification process, andinduced Sc enrichment in the θ (Al2Cu) eutectic. After the homogenization treatment, the majority of coarse nonequilibriumeutectic phases at the grain boundaries dissolved into the α-Al matrix, leading to the relatively uniform distribution ofeach element. Sc-added alloy after homogenization treatments possessed more superior strength and ductility than Sc-freealloy. Compared to the furnace cooling mode, the air cooling mode could inhibit the precipitation of micron-sized coarse T1(Al2CuLi) phase and improve the mechanical properties of the alloys. After homogenization, the continuous Al2Cuphase inthe as-cast Sc-added alloy dissolved and transformed to an array of W-(Al, Cu, Sc) ternary phase, which was identified asAl6Cu6Scwith the body-centered tetragonal structure. The appearance of spherical Al6Cu6Scparticle could not damage themechanical properties of Al–Cu–Li–Mg alloys after the homogenization treatment. The tensile strength, yield strength andelongation of Sc-added alloy after the homogenization by air cooling were 390 MPa, 265 MPa and 10.8%, respectively. Theinvestigation of Al6Cu6Scphase offered a potential avenue to produce high-quality Sc-added 2xxx series alloys.

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