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- 저자 : Shiwei Shi (검색결과 5 건)
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Xiaoxiang Wei,Haibo Zhao,Junjie Yu,Yiming Zhong,Yanlin Liao,Shiwei Shi,Peihong Wang 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.5
The multiple forms of vibration exist in an ambient environment diffusely and already become a considerable object for energy harvesting. However, how to effectively extract low-level, low-frequency, and multi-directional vibration from the ambient environment is becoming a key issue in the field of energy harvesting. To solve this issue, a tower-shaped piezoelectric vibration energy harvester (TS-PVEH) is reported. Finite element simulation indicates that TS-PVEH works in two fundamental modes, i.e., its in-plane and out-of-plane vibration modes. Meanwhile, simulation results show that the natural frequency of TS-PVEH is 3.39 Hz, 3.40 Hz, and 11.50 Hz, respectively; and the experiments also verified that. By virtue of the tower structure of TS-PVEH, the device is pretty sensitive to three-dimensional vibration. At a low level of acceleration 1 m/s 2 , the maximum load power of TS-PVEH is 65.8 μW in out-of-plane mode and 17.2 μW in in-plane mode, respectively. Furthermore, the effects of the PVDF connection mode on the output performance of TS-PVEH were studied in detail, and comparative experimental results show that a reasonable connection of PVDF can improve energy harvesting efficiency. The proposed TS-PVEH is expected to be used to scavenge energy from multi-dimensional, low-level, and low-frequency vibrations that present in an ambient environment.
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Influence of Solution Concentrations on Surface Morphology and Wettability of ZnO Thin Films
Jianguo Lv,Changlong Liu,Feng Wang,Zhitao Zhou,Zhenfa Zi,Yuan Feng,Xiaoshuang Chen,Feng Liu,Gang He,Shiwei Shi,Xueping Song,Zhaoqi Sun 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.2
ZnO thin films were grown on silicon substrates using a hydrothermal method. The XRD patterns show that all of the peaks can be attributed to the wurtzite structures of ZnO. The TC value of (002) plane and average crystal size increase first and then decrease with the increase of solution concentration. SEM and AFM results show that many dense hexagonal cylinder particles have been observed on the surface of the thin films, which grown at 0.08 and 0.10 mol/L. The surface roughness of the thin films deposited at 0.06,0.08, 0.10, and 0.12 mol/L are 24.5, 38.3, 32.0, and 39.4 nm, respectively. Surface wettability results show that the preferential orientation along c-axis and surface roughness contribute significantly to the hydrophobicity. The reversible switching between hydrophobicity and hydrophilicity is related to the synergy of the transition of wetting model, surface crystal structure, and surface roughness.
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Shi, Wei,Han, Jonghoon,Kim, Changwan,Lee, Daeyong,Shin, Hyunkyoung,Park, Hyunchul Elsevier 2015 RENEWABLE ENERGY Vol.74 No.-
<P><B>Abstract</B></P> <P>Korea has huge potential for offshore wind energy and the first Korean offshore wind farm has been initiated off the southwest coast. With increasing water depth, different substructures of the offshore wind turbine, such as the jacket and multipile, are the increasing focus of attention because they appear to be cost-effective. However, these substructures are still in the early stages of development in the offshore wind industry. The aim of the present study was to design a suitable substructure, such as a jacket or multipile, to support a 5 MW wind turbine in 33 m deep water for the Korean Southwest Offshore Wind Farm. This study also aimed to compare the dynamic responses of different substructures including the monopile, jacket and multipile and evaluate their feasibility. We therefore performed an eigenanalysis and a coupled aero-hydro-servo-elastic simulation under deterministic and stochastic conditions in the environmental conditions in Korea. The results showed that the designed jacket and multipile substructures, together with the modified monopile, were well located at soft–stiff intervals, where most modern utility-scale wind turbine support structures are designed. The dynamic responses of the different substructures showed that of the three substructures, the performance of the jacket was very good. In addition, considering the simple configuration of the multipile, which results in lower manufacturing cost, this substructure can provide another possible solution for Korean’s first offshore wind farm. This study provides knowledge that can be applied for the deployment of large-scale offshore wind turbines in intermediate water depths in Korea.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A jacket as well as a multipile substructure was designed to support 5MW OWT for Korean offshore demonstration project in 33 m water depth. </LI> <LI> A fully coupled dynamic analysis was conducted based on Korean environmental conditions. </LI> <LI> The dynamic responses of the three substructures were compared to find their feasibility. </LI> <LI> The jacket had the best performance in terms of the investigated loads. </LI> <LI> The multipile results were comparable with the jacket substructure. </LI> </UL> </P>
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Dynamic Analysis of Three-Dimensional Drivetrain System of Wind Turbine
Shi, Wei,Park, Hyun-Chul,Na, Sangkwon,Song, Jinseop,Ma, Sangjin,Kim, Chang-Wan Korean Society for Precision Engineering 2014 International Journal of Precision Engineering and Vol.15 No.7
In our previous study, a torsional model was used to perform a dynamic analysis of a wind turbine drivetrain. However, detailed characteristics could not be obtained with this torsional model. In this paper, the mathematical model of the wind turbine drivetrain is extended to a three-dimensional dynamic model. A typical arrangement with one low-speed planetary gear stage and two high-speed spur gear stages is used in this work. The governing equation of the drivetrain is derived by using Lagrange's equation. Lagrange's equation takes into account the kinetic energy of each component and potential energies from the shaft, bearing, and gear mesh. The governing equation is solved numerically using direct numerical integration. A dynamic analysis is carried out to investigate the transient response of the drivetrain system.
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