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Ji-ning Song Lin Lu Bin Teng Han-il Park Guo-qiang Tang Hao Wu 《Ocean Engineering》2011,38(11-12):1308-1322
Laboratory tests have been conducted on vortex-induced vibration (VIV) of a long flexible riser towed horizontally in a wave basin. The riser model has an external diameter of 16 mm and a total length of 28.0 m giving an aspect ratio of about 1750. Reynolds numbers ranged from about 3000 to 10,000. Fiber optic grating strain gages are adopted to measure the dynamic response in both cross-flow and in-line directions. The cross-flow vibrations were observed to vibrate at modes up to 6 and the in-line reached up to 12. The fundamental response frequencies can be predicted by a Strouhal number of about 0.18. Multi-mode responses and the asymmetry of the bare pipe response in uniform flow were observed and analyzed. The experimental results confirmed that the riser pipe vibrated multi-modally despite it being subject to a uniform current profile and all of the excited modes vibrated at the Strouhal frequency. The asymmetrical distribution of displacement mainly resulted from the modal composition. Higher harmonics of the VIV response such as the third, fourth and fifth harmonics frequencies were found to be steady over the entire duration of the test even if they varied along the length of the riser pipe. 相似文献
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Zhenghong Tang Samuel D. BrodyRuopu Li Courtney QuinnNan Zhao 《Ocean & Coastal Management》2011,54(5):415-426
Local jurisdictions play a critical role in climate change mitigation and adaptation. This study analyzes the theoretical framework of locally driven climate change actions and uses geographic information system (GIS) to map local jurisdictions’ climate change policy efforts in three Pacific states - California, Oregon, and Washington. The results of our study indicate statistically significant differences in geographic clusters and variations across jurisdictions. An Ordinary Least Squares (OLS) regression model was used to examine climate risk, emission stress, and socioeconomic context variables to detect influence on local climate change policy efforts. The explanatory results indicate that coastal proximity, population density, vehicles emission, and education variables significantly influence local jurisdictions’ climate change actions. The findings contribute to local organizational decision model research and can help local communities to develop more effective climate change policies. 相似文献
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Eko Siswanto Junwu Tang Hisashi Yamaguchi Yu-Hwan Ahn Joji Ishizaka Sinjae Yoo Sang-Woo Kim Yoko Kiyomoto Keiko Yamada Connie Chiang Hiroshi Kawamura 《Journal of Oceanography》2011,67(5):627-650
A bio-optical dataset collected during the 1998?C2007 period in the Yellow and East China Seas (YECS) was used to provide alternative empirical ocean-color algorithms in the retrieval of chlorophyll-a (Chl-a), total suspended matter (TSM), and colored dissolved organic matter (CDOM) absorption coefficients at 440 nm (ag440). Assuming that remote-sensing reflectance (Rrs) could be retrieved accurately, empirical algorithms for TChl (regionally tuned Tassan??s Chl-a algorithm) in case-1 waters (TChl2i in case-2 waters), TTSM (regionally tuned Tassan??s TSM algorithm), and Tag440 or Cag440 (regionally tuned Tassan??s or Carder??s ag440 algorithm) were able to retrieve Chl-a, TSM, and ag440 with uncertainties as high as 35, 46, and 35%, respectively. Applying the standard SeaWiFS Rrs, TChl was not viable in the eastern part of the YECS, which was associated with an inaccurate SeaWiFS Rrs retrieval because of improper atmospheric correction. TChl behaved better than other algorithms in the turbid case-2 waters, although overestimation was still observed. To retrieve more reliable Chl-a estimates with standard SeaWiFS Rrs in turbid water (a proxy for case-2 waters), we modified TChl for data with SeaWiFS normalized water-leaving radiance at 555 nm (nLw555) > 2 mW cm?2 ??m?1 sr?1 (TChl2s). Finally, with standard SeaWiFS Rrs, we recommend switching algorithms from TChl2s (for case-2 waters) to MOCChl (SeaWiFS-modified NASA OC4v4 standard algorithm for case-1 waters) for retrieving Chl-a, which resulted in uncertainties as high as 49%. To retrieve TSM and ag440 using SeaWiFS Rrs, we recommend empirical algorithms for TTSM (pre-SeaWiFS-modified form) and MTag440 or MCag440 (SeaWiFS Rrs-modified forms of Tag440 or Cag440). These could retrieve with uncertainties as high as 82 and 52%, respectively. 相似文献
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Xiaowei Tang Xiwen Zhang Qi Shao Zhenqing Li 《Marine Georesources & Geotechnology》2016,34(6):594-601
In the last 20 years, the bucket foundation has been developed as a new type of offshore platform structure. Because of its short period of application to engineering practices, the theoretical decision on the rotation center and horizontal bearing capacity of the bucket foundation has yet to be agreed. A limit analysis method is used to determine the updated rotation center position and horizontal bearing capacity to evaluate the failure mechanisms of the bucket foundations. The results are compared with numerical simulation and experiments, and also with other theoretical methods. The proposed method can satisfactorily consider the engineering conditions and the result is accurate in determining the rotation center and horizontal bearing capacity. 相似文献
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The Jiaocbang arcuate structure is one of the numerous arcuate structural belts in Sichuan. The present paper gives a further argument about the characteristics of that arcuate structure and the new activity of the Songpinggou fault and affirms that the Songpinggou fault is an active fault in the Holocene epoch. The Diexi M7.5 earthquake took place in 1933 on the west wing of that arcuate structure, near the apex of the arc. Many authors have given quite different opinions about the genetic structure of that earthquake. The authors have made on-the-spot investigations time and again over recent years. Besides this, the authors have also further studied the shape of intensity contour lines, the distribution characteristics of ground surface seismic hazards, the left-lateral dislocation of buildings along the Songpinggou fault, the NWtrending ground fissures that developed on the ground surface after earthquake, and so on. On this basis, it is still considered that the seismogenic fault of the 1933 Diexi M7.5 earthquake was the Songpinggou fault on the west wing of the Jiaochang arcuate structure. 相似文献