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RISS 인기검색어
- 검색키워드
- 저자 : Xu G. Hua (검색결과 4 건)
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Monitoring and control of wind-induced vibrations of hanger ropes of a suspension bridge
Xu G. Hua,Zheng Q. Chen,Xu Lei,Qin Wen,Hua W. Niu 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.23 No.6
In August 2012, during the passage of the typhoon Haikui (1211), large amplitude vibrations were observed on long hangers of the Xihoumen suspension Bridge, which destroyed a few viscoelastic dampers originally installed to connect a pair of hanger ropes transversely. The purpose of this study is to identify the cause of vibration and to develop countermeasures against vibration. Field measurements have been conducted in order to correlate the wind and vibration characteristics of hangers. Furthermore, a replica aeroelastic model of prototype hangers consisting of four parallel ropes was used to study the aeroelastic behavior of hanger ropes and to examine the effect of the rigid spacers on vibration mitigation. It is shown that the downstream hanger rope experiences the most violent elliptical vibration for certain wind direction, and the vibration is mainly attributed to wake interference of parallel hanger ropes. Based on wind tunnel tests and field validation, it is confirmed that four rigid spacers placed vertically at equal intervals are sufficient to suppress the wake-induced vibrations. Since the deployment of spacers on hangers, server hanger vibrations and clash of hanger ropes are never observed.
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Wind-induced responses and dynamic characteristics of a super-tall building under a typhoon event
X. G. Hua,K. Xu,Y.W. Wang,Q. Wen,Z. Q. Chen 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.25 No.1
Wind measurements were made on the Canton Tower at a height of 461 m above ground during the Typhoon <i>Vincente</i>, the wind-induced accelerations and displacements of the tower were recorded as well. Comparisons of measured wind parameters at upper level of atmospheric boundary layer with those adopted in wind tunnel testing were presented. The measured turbulence intensity can be smaller than the design value, indicating that the wind tunnel testing may underestimate the crosswind structural responses for certain lock-in velocity range of vortex shedding. Analyses of peak factors and power spectral density for acceleration response shows that the crosswind responses are a combination of gust-induced buffeting and vortex-induced vibrations in the certain range of wind directions. The identified modal frequencies and mode shapes from acceleration data are found to be in good agreement with existing experimental results and the prediction from the finite element model. The damping ratios increase with amplitude of vibration or equivalently wind velocity which may be attributed to aerodynamic damping. In addition, the natural frequencies determined from the measured displacement are very close to those determined from the acceleration data for the first two modes. Finally, the relation between displacement responses and wind speed/direction was investigated.
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Grace G.L. Yue,Sau-Wan Cheng,Hua Yu,Zi-Sheng Xu,Julia K.M. Lee,Po-Ming Hon,Mavis Y.H. Lee,Edward J. Kennelly,Gary Deng,Simon K. Yeung,Barrie R. Cassileth,Kwok-Pui Fung,Ping-Chung Leung,Clara B.S. Lau 한국식품영양과학회 2012 Journal of medicinal food Vol.15 No.3
The rhizome of Curcuma longa (turmeric) is often used in Asia as a spice and as a medicine. Its most wellstudied component, curcumin, has been shown to exhibit poor bioavailability in animal studies and clinical trials. We hypothesized that the presence of lipophilic components (e.g., turmerones) in turmeric extract would affect the absorption of curcumin. The effects of turmerones on curcumin transport were evaluated in human intestinal epithelial Caco-2 cells. The roles of turmerones on P-glycoprotein (P-gp) activities and mRNA expression were also evaluated. Results showed that in the presence of a- and aromatic turmerones, the amount of curcumin transported into the Caco-2 cells in 2 hours was significantly increased. a-Turmerone and verapamil (a P-gp inhibitor) significantly inhibited the efflux of rhodamine-123 and digoxin (i.e.,inhibited the activity of P-gp). It is interesting that aromatic turmerone significantly increased the rhodamine-123 efflux and Pgp (MDR1 gene) mRNA expression levels. The effects of a- and aromatic turmerones on curcumin transport as well as P-gp activities were shown here for the first time. The presence of turmerones did affect the absorption of curcumin in vitro. These findings suggest the potential use of turmeric extract (including curcumin and turmerones), rather than curcumin alone, for treating diseases.
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Monitoring of wind turbine blades for flutter instability
Chen, Bei,Hua, Xu G.,Zhang, Zi L.,Basu, Biswajit,Nielsen, Soren R.K. Techno-Press 2017 Structural monitoring and maintenance Vol.4 No.2
Classical flutter of wind turbine blades indicates a type of aeroelastic instability with fully attached boundary layer where a torsional blade mode couples to a flapwise bending mode, resulting in a mutual rapid growth of the amplitudes. In this paper the monitoring problem of onset of flutter is investigated from a detection point of view. The criterion is stated in terms of the exceeding of a defined envelope process of a specific maximum torsional vibration threshold. At a certain instant of time, a limited part of the previously measured torsional vibration signal at the tip of blade is decomposed through the Empirical Mode Decomposition (EMD) method, and the 1st Intrinsic Mode Function (IMF) is assumed to represent the response in the flutter mode. Next, an envelope time series of the indicated modal response is obtained in terms of a Hilbert transform. Finally, a flutter onset criterion is proposed, based on the indicated envelope process. The proposed online flutter monitoring method provided a practical and direct way to detect onset of flutter during operation. The algorithm has been illustrated by a 907-DOFs aeroelastic model for wind turbines, where the tower and the drive train is modelled by 7 DOFs, and each blade by means of 50 3-D Bernoulli-Euler beam elements.
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